Remove spew from matrix test.
Must clone Cursor.set to ensure we have type info to parallelize its calls.
Whitespace fix.
Uint8 clamping is safe for parallel execution.\
Manually cloning the test driving routine via cut-and-paste.

Manually cloning the code since parallization will currently fail if
you attempt to parameterize over distinct typed-array consructor.

(We are discussing removing that latter limitation by adding an
inline-cache for UnsafePutElements, analogously to how we have one for
get operations.
Bug fix: need to pass source (== self) argument to map callback.

The source argument goes before the outptr, for maximal compatibility
with existing map interface.
Moved typed-array buildArray class method to helper functions file.
Added 1d matrix map tests; fixed bug found via spec-driven test writing.