crt: Unify kernel32.def for lib64 and libarm32

Keep functions from both versions that were missing on the other
ones.

Include *Ums* functions only for x86_64, based on annotations
in kernel32.spec in wine.

Keep manually commented out functions as they were. Include
__chkstk on arm though.

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