manifest.c: ensure realloc_if_full() returns 1 or 0
This fixes an MSVC 2008 warning that I don't see with gcc 4.6.3-2:
warning C4047: 'return' :
'bool' differs in levels of indirection from 'line *'
More importantly, the truncation from pointer to 'unsigned char' would have
returned 0 if self->lines pointed to an address divisible by 0xFF, which causes
find_lines() to return MANIFEST_OOM. I was able to cause this to happen in a
trivial program with the gcc compiler.
$ echo 'raise Exception("bit bucket overflow")' > badext.py
$ abspath=`pwd`/badext.py
$ cat <<EOF >> $HGRCPATH
> [extensions]
> gpg =
> hgext.gpg =
> badext = $abspath
> badext2 =
> EOF
$ hg -q help help
*** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow
*** failed to import extension badext2: No module named badext2
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