Changes to 7z_C source
----------------------
I made several minor changes:

* Hard-coded setup to _SZ_ONE_DIRECTORY, _LZMA_IN_CB, _LZMA_LOC_OPT

* Fixed several memory free functions to not access NULL when cleaning
up after a failed allocation.

* Made private functions static.

* Fixed SzArchiveOpen to properly report error when header can't be
read.

* Fixed glaring conflicts between LzmaTypes.h and 7zTypes.h.

-- 
Shay Green <gblargg@gmail.com>
