crt: msvcrt.def.in: Fix definitions of _ctype and _mbcasemap symbols

Both symbols refers to global variable, not the function. So mark them with
DATA for all platforms. gendef detects that _mbcasemap is DATA for all I386
versions of msvcrt.dll (Visual C++ 5.0, 6.0, Win9x, 2000, XP, ... up to 10).
But gendef since Windows XP version of msvcrt.dll cannot autodetect that
_ctype is DATA symbol.

Signed-off-by: Martin Storsjö <martin@martin.st>