Added the NativeInt and NativeWord structure aliases to provide a portable way to refer to the native numeric types in signatures.

Reimplementation of the Random structure to use the Mersenne Twister algorithm. There are both 32-bit and 64-bit versions of the generator (which one is included depends on the target platform).

Reworked the code for determining the maximum hash-table size (used in the HashSetFn and HashTableRep modules) so that it does not depend on Int.int and Word.word being the same size (an issue for MLton). Also split that code out into the internal MaxHashTableSize module.

Added support for the end-of-line assertion ("$") and full support for intervals to the Thompson engine in the RegExp library.

Added modules for the representation of booleans, integers, and words as hash-consed values to the HashCons library.

Reworked the UTF8 structure to impose stricter validation of the encodings (Issue 276).

Modified the JSON.json datatype to include the INTLIT of string constructor (this change is to support future improvements to the JSON parsers).