tests/test-revert-flags.t

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.

#require execbit

  $ hg init repo
  $ cd repo
  $ echo foo > foo
  $ chmod 644 foo
  $ hg ci -qAm '644'

  $ chmod 755 foo
  $ hg ci -qAm '755'

reverting to rev 0

  $ hg revert -a -r 0
  reverting foo
  $ hg st
  M foo
  $ hg diff --git
  diff --git a/foo b/foo
  old mode 100755
  new mode 100644

  $ cd ..