harden and speed up path op unit tests

harden and speed up path op unit tests

PathOps tests internal routines direcctly. Check to make sure that
test points, lines, quads, curves, triangles, and bounds read from
arrays are valid (i.e., don't contain NaN) before calling the
test function.

Repurpose the test flags.
- make 'v' verbose test region output against path output
- make 'z' single threaded (before it made it multithreaded)

The latter change speeds up tests run by the buildbot by 2x to 3x.

BUG=

Committed: https://code.google.com/p/skia/source/detail?r=10107

[caryclark, 2013-07-16 16:11:34]

Committed patchset #2 manually as r10107 (presubmit successful).