Add FFI conversions for C types
Conversions are added to the structure Foreign for C types as follows:
(signed) long long cLonglong, cLonglongLarge unsigned long long cUlonglong, cUlonglongLarge ptrdiff_t cPtrdiff, cPtrdiffLarge intptr_t cIntptr, cIntptrLarge uintptr_t cUintptr, cUintptrLarge