use caret requirements for dependencies

This way the deps that are below 1.0 will only be updated
at the patch level, and the ones >= 1.0, at the patch and
minor levels.
Fixes: rust-vmm#199.
Also updated vmm-sys-util to latest version available.

Signed-off-by: Laura Loghin <[email protected]>

Author: lauralt

Cargo.toml

@@ -18,17 +18,17 @@ backend-mmap = []
 backend-atomic = ["arc-swap"]
 
 [dependencies]
-libc = ">=0.2.39"
-arc-swap = { version = ">=1.0.0", optional = true }
+libc = "0.2.39"
+arc-swap = { version = "1.0.0", optional = true }
 
 [target.'cfg(windows)'.dependencies.winapi]
-version = ">=0.3"
+version = "0.3"
 features = ["errhandlingapi", "sysinfoapi"]
 
 [dev-dependencies]
 criterion = "0.3.0"
-matches = ">=0"
-vmm-sys-util = ">= 0.4.0"
+matches = "0"
+vmm-sys-util = "0.10.0"
 
 [[bench]]
 name = "main"