fix easylogo on big endian dev systems

didnt realize how out of shape easylogo actually was until i tried using it.
this patch does byte swapping as need be on the input tga header since the tga
is in little endian but the host could just as well be big endian.  i didnt
bother using bswap macros or such stuff from system headers as nothing in
POSIX dictates byte swapping functionality.

Signed-Off-By: Mike Frysinger <vapier@gentoo.org>