Add union pointer specification for `UI.WindowsAndMessaging` constants

[Tired-Fox]

Fixes issue #30: _Ability to define alignment/unionpointer constants similar to function params

• Add ability to specify constants as union pointers.
• Update std.os.exit to std.process.exit to allow code to build with zig v0.12.0-dev.3496+a2df84d0f
• Update removeCr to be able to be called at comptime with zig v0.12.0-dev.3496+a2df84d0f
• Remove constant skips for IDC_*, IDI_*, and RT_* variables
• Add union pointer specification for IDC_*, IDI_*, and RT_* constants and add the corresponding function arguments that expect these constants as union pointers as well.

[marler8997]

Great work, thanks for the contribution!

Here's a commit showing the diff of zigwin32 as a result of this change: https://github.com/marlersoft/zigwin32/commit/2f0fbd0897411ab43e574785cacd5d2fcc674506