Add API calls equivalent to existing calls that use an absolute timeout
as opposed to a relative timeout.  The absolute timeout can support
resolution of 0.1 usec in the default configuration.

Internally this primarily affects the underlying call to select().

Note that per the definition of select() in POSIX, it uses a
"struct timeval" which has a resolution of 1 usec.

…mments

This commit addresses issues flagged during static analysis by:
- Adding JSC 2.1 disposition comments.
- Making OS_strnlen publicly accessible and replacing strlen with it.

Calls to "OS_strnlen" are likely needed to return an actual length,
so make a default handler that does return a length.  The value
may still be overridden in tests, though.

Fix #1455, High-res timed stream ops

Fix #1458, Moves OS_strnlen to public API and adds static analysis comments

…e incorrect status variable.

Fix #1455, High-res timed stream ops