Prepare 3.51 from git

Add git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git submodule

git submodule add \
	git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git man-pages-git
Remove po4a-fixes.patch for man4/random.4

Fixed upstream in 7b512dfff43391f33233b85c55791f8ce8aa3abe
Add po4a-fixes.patch to fix groff errors in proc.5
Revert "Add po4a-fixes.patch to fix groff errors in proc.5"

This reverts commit 323b77023dc7dd927f53a4a2668e40bad4bbccc1.

Fixed upstream by 182090db9695cdb86a78 "proc.5: ffix"
Remove man-pages-git submodule and set V to 3.51
unistd.cfg: Add groff_code=verbatim option when processing syscall.2

An .if macro has been added into text, so this option is now needed.
Add README.JM
Merge remote-tracking branch 'upstream/master'