Fix build errors on GCC < 4.2
Let to be failed if no suituable python version.
fixes again, for the case pkgsrc openssl is prefered than builtin old openssl.
GCC >= 4.4 is not required for architectures without ssse3.
Fix packaging with python-3.4
Fix typo in previous.
SA56624 is CVE-2014-1912.
threads supports for OpenBSD (not completed yet)
PR pkg/48786
prevent to overwrite CC on NetBSD.
Changes 1.9.3:
* "git p4" dealing with changes in binary files were broken by a
   change in 1.9 release.
* The shell prompt script (in contrib/), when using the PROMPT_COMMAND
  interface, used an unsafe construct when showing the branch name in
  $PS1.
* "git rebase" used a POSIX shell construct FreeBSD /bin/sh does not
  work well with.
* Some more Unicode codepoints defined in Unicode 6.3 as having
  zero width have been taught to our display column counting logic.
* Some tests used shell constructs that did not work well on
  FreeBSD.
Hack for PR pkg/48500 is also required by OpenBSD-*-alpha.