A preprocessor macro definition was overwriting a C variable name.

Capitalized the preprocessor defs 'lil_endian', 'big_endian', 'lil_ieee', and 'big_ieee' to avoid trampling on an unrelated 'big_endian' variable in src/asf_view/read_envi.c, and also to conform to standard practice for cpp defs.
Merge pull request #131 from ninneman/devel

A preprocessor macro definition was overwriting a C variable name.