Change GMPs default PRNG to Mersenne Twister

Since we don't allow users to seed the RNG, there is no BC issue with changing the generator.
Add gmp_random_bits(bits) and gmp_random_range(min, max)
Add test files
Mersenne Twister was added in GMP 4.2
Make sure min < max
Address issues raised by @nikic

 - Thread safety on rand init function.
 - Ret false on validation failure
 - Add _dep of temp_a to temp_b
 - Special case int sized min values
 - More tests!
Merge branch 'PHP-5.6' of https://github.com/php/php-src into gmp-random
Upated NEWS
More fixes for nodelist array access
- testing for null property read
- no zval copying if the type is already long
- memory fix for master
Merge branch 'PHP-5.6'

* PHP-5.6:
  More fixes for nodelist array access
  - testing for null property read
  - no zval copying if the type is already long
  - memory fix for master
  - use zend_long for offset

Conflicts:
	ext/dom/php_dom.c
DLL export several APIs needed for phpdbg
Merge branch 'PHP-5.6'

* PHP-5.6:
  DLL export several APIs needed for phpdbg
Remove retval member in spl_dllist

Seems pretty useless, unless I'm missing something?
Fix invalid zend_string_frees in reflection

zend_lookup_class can share the name
Fix ::jsonSerialize() failure message
Fix incdec of referenced properties

I thought these SEPARATE_ZVAL_IF_NOT_REF usages were safe at first,
because incdec op supports reference variables. However this
violates the constraint that IS_TMP_VAR variables may not be
references (which is an issue if you use the result of the incdec
op).

Still need to fix the cases where read_property/write_property is
used.
Ensure __LINE__ is always accurate
We can't eliminate FETCH_CONSTANT opcodes for constants represented by AST.
Merge branch 'PHP-5.6'

* PHP-5.6:
  We can't eliminate FETCH_CONSTANT opcodes for constants represented by AST.

Conflicts:
	ext/opcache/Optimizer/pass1_5.c
Deref right value for compound assign ops

Currently we do not support IS_REFERENCE operands for most of our
*_function's (should we?), so we need to deref here.