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!
Fixed a bug that causes crash when environment variable is access while parsing php.ini
Merge branch 'PHP-5.6' of https://github.com/php/php-src into gmp-random
Upated NEWS
Add 64 bit formats to pack() and unpack()
RFC: 64 bit format codes for pack() and unpack()
Merge branch 'PHP-5.6'

* PHP-5.6:
  Add 64 bit formats to pack() and unpack()
pack(): Use SIZEOF_ZEND_LONG instead of SIZEOF_LONG
Added note to UPGRADING regarding 64-bit support in pack()/unpack()
update NEWS

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Merge branch 'PHP-5.4' into PHP-5.5
update NEWS

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Merge branch 'PHP-5.5' into PHP-5.6
update NEWS

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Merge branch 'PHP-5.6'