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.
Why would you export (and call, above) a helper function? Seems StrAlloc and StrAllocSecure should call into StrCoreAlloc (as you are) but leave it as a defined function with strutil.cpp.