Fix.dwarf error bad symbol mangling (#2127)

Don't escape '.' in asm symbols for DWARF

Author: poechsel

backend/asm_targets/asm_symbol.ml

@@ -25,7 +25,7 @@
  **********************************************************************************)
 
 let should_be_escaped = function
-  | 'A' .. 'Z' | 'a' .. 'z' | '0' .. '9' | '_' -> false
+  | 'A' .. 'Z' | 'a' .. 'z' | '0' .. '9' | '_' | '.' -> false
   | _c -> true
 
 module Thing = struct