endian.h: Added automatic endian detection support
endian.h: Added a AUTO_DETECT_PLATFORM define to override auto-detect

This is done to prevent strange cases where the auto detect isn't working
correctly even though it should be
Makefile: Added support for platform autodetection

This auto-detection support does not preclude explicit declaration in the cases
where auto-detect goes goofy and doesn't work correctly.
Merge pull request #14 from DrItanium/platform-autodetect

Added automatic platform detection support