Win32: modify g_open()/g_fopen() to allow removing/renaming of open files

This brings the semantic of open files more in line with POSIX. g_open() and
g_fopen() now call CreateFileW directly. This change removes the support for
MSVCRXX mode-string extensions for g_fopen().

Closes #539
6 jobs for akruis_glib#539 in 13 minutes and 22 seconds (queued for 6 seconds)
latest
Status Name Job ID Coverage
  Build
passed fedora-meson-android_ndk_r16_api21_arm64 #46760

00:05:21

passed fedora-meson-mingw64 #46761

00:06:06

passed fedora-meson-x86_64 #46759

00:07:12

passed msys2-mingw32 #46762
win32

00:07:39

passed vs2017-x64 #46763
win32

00:05:30

 
  Coverage
passed coverage #46764

00:05:43

76.8%