[FREELDR] Small code re-organization for the "ntldr" sub-module.

[FREELDR] Small code re-organization for the "ntldr" sub-module.

Split the "main" winldr.h header into the one containing global code
that actually doesn't really depend on the "windows" NT loader part,
and one that actually concerns code just for the NT Loader.
The latter goes into "ntldr".

svn path=/branches/setup_improvements/; revision=74743