StrCoreAlloc* and StrAlloc*Secure

Rename the StrAllocate* functions to StrCoreAlloc* to make it easier to tell them apart from the original StrAlloc* methods.

Add the StrAlloc*Secure methods back as wrappers around the StrCoreAlloc* functions.
I'm with @barnson. StrCoreAlloc feels like it should be static (private) and not expand the API surface. The BOOL at the end is too subtle for the security decision being made, IMHO.