Enabled PRNG peripheral in PIC32MZ for random(...) functions.

The PIC32MZ has a built-in cryptographically secure pseudo random number generator.  This patch allows the random(x) and random(x,y) functions to use this PRNG instead of the usual software based one.  When the True Random Number Generator in the PIC32MZ is also working (when they fix it) it can be used to seed the hardware PRNG with a true random number.