crt: Fix exports of crtdll.dll library

Symbols _ctype and _mbctype are DATA, like in all other crt libraries.
Symbol _onexit is read-only function. And symbols _mkgmtime, _mkgmtime32
and _mkgmtime64 are not present in crtdll.dll at all. Calling gendef on
crtdll.dll from Win NT 3.50 and Win 7 confirms it.

Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-crt/lib32/crtdll.def

diff --git a/mingw-w64-crt/lib32/crtdll.def b/mingw-w64-crt/lib32/crtdll.def
index fed70ff..4864025 100644
--- a/mingw-w64-crt/lib32/crtdll.def
+++ b/mingw-w64-crt/lib32/crtdll.def
@@ -245,7 +245,7 @@
 _cputs
 _creat
 _cscanf
-_ctype
+_ctype DATA
 _cwait
 _daylight_dll DATA
 _daylight DATA == _daylight_dll
@@ -374,7 +374,7 @@
 _mbctolower
 _mbctombb
 _mbctoupper
-_mbctype
+_mbctype DATA
 _mbsbtype
 _mbscat
 _mbschr
@@ -414,13 +414,10 @@
 _memccpy
 _memicmp
 _mkdir
-_mkgmtime DATA
-;_mkgmtime32 = _mkgmtime
-_mkgmtime64
 _mktemp
 _msize
 _nextafter
-_onexit DATA
+_onexit
 _open
 _open_osfhandle
 _osmajor_dll DATA