Description:
------------
There are many non-cryptographic applications using the rand function of PHP and I was wondering if it is worth the effort to implement a call to the hardware function RDRND if it is supported by the platform.

Benefits of using RDRND:
* It is seeded with a true random number generator.
* Better source of random numbers than Mersenne Twister algorithm.

Concerns of using RDRND:
* This operand is available on recent Intel CPUs (Ivy Bridge) and only in the coming Zen AMD Architecture.
* A bit slower than Mersenne Twister (if we omit the time it takes to seed the algo from the benchmark).

Benefits of current PHP implementation:
* The code is faster than RDRND if we don't count the generation of the seed number.

Concerns of current PHP implementation:
* A hard-coded limit of a 32 bits integer causes the need of two calls and a shift of the result so as to create a 64 bits number.
* If the generator is not seeded, the PHP makes a syscall in order to get the PID of PHP, whereas RDRND is seeded.
* Maybe considered as obsolete (see #67795).

The implementation (ext/standard/mt_rand.c) would look like

#ifdef __RDRND__
#include <immintrin.h>
// No need to call GENERATE_SEED()
#	ifdef ZEND_ENABLE_ZVAL_LONG64
// Call to _rdrand64_step(uint64_t*);
#	else
// Call to _rdrand32_step(uint32_t*);
#	endif
#else
//current PHP implementation
#endif