add root/checkedint.h and .c
Fix Issue 13212 - Windows line endings handled incorrectly by ddoc macros

Handle \r as \n in macro definitions to prevent a trailing carriage
return on a macro with an empty line following it.
Fix Issue 12745 - [Ddoc] Underscore is removed from numbers
COFF support for Win32, use command line option -m32coff
use bool "coff" instead of objfmt in the frontend
Test 2 underscores
Add DirectX library path

64-bit only. If 32-bit COFF support is ever added we can add that to the `Environment32` section as well.

Fixes #13265
Fix counting unittest indent with Windows line endings
Fix removing trailing whitespace in documented unittest (Windows)
Fix reading ddoc ESCAPES on Windows
fix Issue 13204 - recursive alias declaration
fix Issue 2427 - Function call in struct initializer fails to compile
fix Issue 2438 - Cannot get types of delegate properties
fix Issue 4225 - forward reference of opCall (mangle.c:81: char* mangle(Declaration*): Assertion `fd && fd->inferRetType' failed.)
fix Issue 4423 - [tdpl] enums of struct types
fix Issue 6699 - More cases of __error in error messages
fix Issue 7477 - Enum structs without specified values
fix Issue 10629 - [ICE](dt.c 106) with void array
fix Issue 10928 - Fails to create closures that reference structs with dtor
fix Issue 13217 - nothrow, template function and delegate: compilation error