d98e087042
Integrate the bsdiff code into imgdiff so we can just call it rather than writing temp files and invoking bsdiff as a subprocess. When computing multiple patches from the same source file, we can also save time by doing some bsdiff preprocessing on the source file only once. (Note this renames the existing 'bsdiff.c' -- which actually does patching in applypatch -- to 'bspatch.c', and introduces a new bsdiff.c linked into imgdiff.)