Summary: Also brings in some cleanups from JDK-8048123
Reviewed-by: rriggs, chegar, phh, clanger, aph

8207152: Placeholder for Japanese new era should be two characters
8211398: Square character support for the Japanese new era
8180469: Wrong short form text for supplemental Japanese era
8206120: Add test cases for lenient Japanese era parsing
8218915: Change isJavaIdentifierStart and isJavaIdentifierPart to handle new code points
8217710: Add 5 currency code points to Java SE 8uX
Reviewed-by: coffeys, naoto
Contributed-by: deepak.kejriwal@oracle.com

Reviewed-by: darcy, weijun