Turn on the Region JIT (take 2)

Except for ARM.

Reviewed By: @swtaarrs

Differential Revision: D1119650
PHP_VERSION_ID should not be greater than all Zend

PHP_VERSION_ID is now 504999 which is > all Zend versions which
makes using it for comparisons of less than 5.5/5.6/etc. impossible.

Closes #1603

Reviewed By: @sgolemon

Differential Revision: D1135461
Disable flaky zend test

Reviewed By: @bertmaher

Differential Revision: D1135985
Rename Interval::info -> loc in xls.cpp

Leftover from the RegisterInfo->PhysLoc rename.

Reviewed By: @bertmaher

Differential Revision: D1135841