Fix LE/BE_INT() and BYTE_SWAP_INT() for 64-bit long targets (Linux-x64)

long is 64-bits (8 bytes), not 32-bit on some target platforms (e.g. Linux-x64), so don't assume sizeof(long)==4.

It appears we weren't using these "automatic" integer-size macros anywhere that I can see, so no harm, but might as well fix them.

Also remove BYTE_SWAP_SHORT and BYTE_SWAP_LONG since they're terribly named. Retain the LE/BE_SHORT/LONG macros since we're using them currently in SBBS (e.g. js_file.c).