StrAlloc*Secure

Rename the StrAllocate* functions to Alloc*Helper to make it easier to tell them apart from the original StrAlloc* methods, and don't export them.

Add the StrAlloc*Secure methods back as wrappers around the Alloc*Helper functions.

Create wrapper functions in variable.cpp around StrAlloc* and StrAlloc*Secure.  Putting them in variable worked out, since VariableStrAlloc* means it's variable which StrAlloc* gets called :)