Prepare 3.53 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

Sync to upstream 343a2c3b.

Set V=3.53-git
Remove man-pages-git submodule and set V to 3.53
Add restart_syscall.2 into signal
Merge remote-tracking branch 'upstream/master'