Use wmain() if supported by the compiler/CRT instead of main().

Use wmain() if supported by the compiler/CRT instead of main().

This avoids a needless conversion from (originally Unicode) command line to
ANSI by the CRT and conversion back by wxWidgets and, especially, ensures that
there is no data loss if the Unicode command line arguments can't be converted
into the current charset.

See #14580.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72402 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775