Merge branch 'PHP-5.6' of git.php.net:php-src into PHP-5.6

* 'PHP-5.6' of git.php.net:php-src:
  Fixed bug #65199 (Wrong Day of Week) and fixed bug #63391 (Incorrect/inconsistent day of week prior to the year 1600)
  Marking those two as XFAIL for now.
  Fixed a few DST changeover issues.
  Move add/sub to timelib.
  Fix backwards transition diffs.
  Split up tests into their different categories.
  Group those tests a bit better, as some of the bd ones wanted a "ST" feature that doesn't exist yet.
  Fixed forward transitions in diffs.
  Always reset those parameters.
  Fixed "Forward Transition" construction of DateTime objects.
Remove duplicate / commented code in GMP
Use class handlers for GMP serialization

A bit faster and less boilerplate
Add gmp_root() and gmp_rootrem() functions
Clean up GMP arginfos

Removed duplicate arginfos, specified number of required args
everywhere and removed weird pass-by-ref arguments.
Merge branch 'PHP-5.6'