Problem:

1. some platforms do not have inttypes.h, and chasing them down
   becomes ridiculous.  Therefore, uint64_t can't be used for 64-bit
   values.
2. some (other) platforms do not support "long long".

Solution: make AEP_U64 a struct with two longs unless long already is
64 bit long.

Also, restore all other types back to use unsigned char, unsigned int
and unsigned long.  Make sure that AEP_U32 actually becomes 32 bits,
even on platforms where long is 64 bits (actually, we're just guessing
that int will stay at 32 bits on those...).