signed/unsigned mismatch warning

[John A Meinel]

This is just a small warning I don't want to forget about:
_groupcompress_pyx.c
bzrlib/_groupcompress_pyx.c(1288) : warning C4018: '>' : signed/unsigned mismatch
bzrlib/_groupcompress_pyx.c(1290) : warning C4018: '>' : signed/unsigned mismatch
C:\Program Files\Microsoft Visual Studio 9.0\VC\BIN\cl.exe /c /nologo /Ox /MD /W3
N32 -Ic:\Python26\include -Ic:\Python26\PC /Tcbzrlib/diff-delta.c /Fobuild\temp.wi
rlib/diff-delta.obj
diff-delta.c
bzrlib/diff-delta.c(954) : warning C4018: '>' : signed/unsigned mismatch
bzrlib/diff-delta.c(961) : warning C4018: '<' : signed/unsigned mismatch

I doubt it will effect anything, but I'd like to write a small patch to fix this.