Verify java.util.regex.Pattern vs. OpenJDK 8u121-b13, step 3.

This CL mostly adds or tweaks change markers; only minimal code
refactorings (no behavior change) are made to minimize the diff
vs. upstream.

Documentation for the binary property / character class
\p{IsJoin_Control} is added by this CL (consistent with other
documented binary properties), although these binary properties
do not currently work as documented. Fixing this up is left to a
follow-up CL (bug 110364810).

Note that before this CL, compile(String, int) vs. compile(String)
where inconsistent with respects to whether or not they carried a
"throws PatternSyntaxException clause. This CL removes it, which
is consistent with upstream.
Note that there is still a @throws clause in the documentation and
behavior has not changed.

Test: CtsLibcoreTestCases
Bug: 109659282

Change-Id: I1aa8c056955f3052b17c983b52f080c2bccc3943