Overhaul the library with autogenerated code.

This change overhauls ImGui.NET to be almost entirely auto-generated.
It parses data files from cimgui, which contain pre-processed
information about Dear ImGui's structures, enums, and functions. The
code generator spits out identical C# types and functions, and also
generates a safe, friendly wrapper layer.

--- This is a combination of 22 commits. ---

Initial attempt at auto-generating the native bindings.

More WIP generator stuff.

Mostly-working bindings with some TODO's left.

More WIP stuff for safe wrappers and bindings.

WIP

Update cimgui definitions and even better safe wrappers.

Fix "nonUDT" overloads and add a "RangeAccessor" struct.

Remove constructor methods from wrapper types.

More WIP

Grab latest structs_and_enums.json file

Attempted improvements

Very good state, everything working.

Correct cimgui.dll (win-x64)

Rework how ref/out parameters are marshalled.

Remove problematic string begin/end parameter pairs.

Update native deps to 1.0.65, update ImGui.NET.csproj.

Fix sample program compilation.

Fix up XNA sample program with new binding changes.

Add several more manual ImGui overloads to ease the upgrade.

Add [Flags] to flags enums.

Change version to 1.65.0.

Capitalize "Dear ImGui".

Author: mellinoe

.gitignore

@@ -256,4 +256,7 @@ Session.vim
 *.VC.db
 
 # Rider/Jetbrains IDEs
-.idea
+.idea
+
+# download dir
+deps/

deps/cimgui/linux-x64/cimgui.so

@@ -0,0 +1,65 @@
+param (
+    [Parameter(Mandatory=$true)][string]$tag
+)
+
+Write-Host Downloading native binaries from GitHub Releases...
+
+if (Test-Path $PSScriptRoot\deps\cimgui\)
+{
+    Remove-Item $PSScriptRoot\deps\cimgui\ -Force -Recurse | Out-Null
+}
+New-Item -ItemType Directory -Force -Path $PSScriptRoot\deps\cimgui\linux-x64 | Out-Null
+New-Item -ItemType Directory -Force -Path $PSScriptRoot\deps\cimgui\osx-x64 | Out-Null
+New-Item -ItemType Directory -Force -Path $PSScriptRoot\deps\cimgui\win-x86 | Out-Null
+New-Item -ItemType Directory -Force -Path $PSScriptRoot\deps\cimgui\win-x64 | Out-Null
+
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+$client = New-Object System.Net.WebClient
+$client.DownloadFile(
+    "https://github.com/mellinoe/imgui.net-nativebuild/releases/download/$tag/cimgui.win-x86.dll",
+    "$PSScriptRoot/deps/cimgui/win-x86/cimgui.dll")
+if( -not $? )
+{
+    $msg = $Error[0].Exception.Message
+    Write-Error "Couldn't download x86 cimgui.dll. This most likely indicates the Windows native build failed."
+    exit
+}
+
+Write-Host "- cimgui.dll (x86)"
+
+$client.DownloadFile(
+    "https://github.com/mellinoe/imgui.net-nativebuild/releases/download/$tag/cimgui.win-x64.dll",
+    "$PSScriptRoot/deps/cimgui/win-x64/$configuration/cimgui.dll")
+if( -not $? )
+{
+    $msg = $Error[0].Exception.Message
+    Write-Error "Couldn't download x64 cimgui.dll. This most likely indicates the Windows native build failed."
+    exit
+}
+
+Write-Host "- cimgui.dll (x64)"
+
+$client.DownloadFile(
+    "https://github.com/mellinoe/imgui.net-nativebuild/releases/download/$tag/cimgui.so",
+    "$PSScriptRoot/deps/cimgui/linux-x64/cimgui.so")
+if( -not $? )
+{
+    $msg = $Error[0].Exception.Message
+    Write-Error "Couldn't download cimgui.so. This most likely indicates the Linux native build failed."
+    exit
+}
+
+Write-Host - cimgui.so
+
+$client.DownloadFile(
+    "https://github.com/mellinoe/imgui.net-nativebuild/releases/download/$tag/cimgui.dylib",
+    "$PSScriptRoot/deps/cimgui/osx-x64/cimgui.dylib")
+if( -not $? )
+{
+    $msg = $Error[0].Exception.Message
+    Write-Error "Couldn't download cimgui.dylib. This most likely indicates the macOS native build failed."
+    exit
+}
+
+Write-Host - cimgui.dylib

deps/cimgui/osx-x64/cimgui.dylib

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace CodeGenerator
+{
+    class CSharpCodeWriter : IDisposable
+    {
+        private readonly StreamWriter _sw;
+        private int _indentLevel = 0;
+
+        public CSharpCodeWriter(string outputPath)
+        {
+            _sw = File.CreateText(outputPath);
+        }
+
+        public void Using(string ns)
+        {
+            WriteIndented($"using {ns};");
+        }
+
+        public void PushBlock(string blockHeader)
+        {
+            WriteIndented(blockHeader);
+            WriteIndented("{");
+            _indentLevel += 4;
+        }
+
+        public void PopBlock()
+        {
+            _indentLevel -= 4;
+            WriteIndented("}");
+        }
+
+        public void WriteLine(string text)
+        {
+            WriteIndented(text);
+        }
+
+        private void WriteIndented(string text)
+        {
+            for (int i = 0; i < _indentLevel; i++)
+            {
+                _sw.Write(' ');
+            }
+            _sw.WriteLine(text);
+        }
+
+        public void Dispose()
+        {
+            _sw.Dispose();
+        }
+    }
+}

deps/cimgui/win-x64/cimgui.dll

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Content Include="structs_and_enums.json" CopyToOutputDirectory="PreserveNewest" />
+    <Content Include="definitions.json" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
+  </ItemGroup>
+
+</Project>