Add m68k to recognized CPUs (machinetype)
Add amigaos to recognized operating systems (osversion)
Add ability to override "config.guess" output w/ LDEARCH= to osversion
Add platform.h clauses to recognize AmigaOS 3 using gcc to cross-compile
* Address older versions of C compiler which don't have __BYTE_ORDER__
* Checking for __GNUC__ is not sufficient to determine if builtins are available.
* Add makefile fragment for 32-bit PowerPC on Mac OSX build, and ignore the build directories.
* Add comment describing use of __BIG/LITTLE_ENDIAN__ definition
Rather than having to specify or omit -DBYTESWAP in the Makefile
fragment for each system we can detect whether the system requires
byte swapping based on the __BYTE_ORDER__ C preprocessor definition.
Update CMakeLists.txt to account for this as well.
This also adds a bit to the `-info` output to say which OS and CPU
are being targeted.
This can be used in subsequent commits to drive whether or not
we need `BYTESWAP` and whether or not unaligned memory access
is okay.
We'll be able to remove per-platform defines from all of the
makefiles and cmake.
