RFR: JDK-8042589: String.toLowerCase do not work for some concatenated strings

[Xueming Shen]

Hi,

Please help review the change for JDK-8042589.

Issue:    https://bugs.openjdk.java.net/browse/JDK-8042589
webrev: http://cr.openjdk.java.net/~sherman/8042589/webrev/

This is a regression caused by the following change for #JDK-8032012,

issue:    https://bugs.openjdk.java.net/browse/JDK-8032012
webrev: http://cr.openjdk.java.net/~sherman/8032012/
discussion: http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-February/024862.html

It appears the last optimization for the surrogates we pushed in is
incomplete. We still need to check isSurrogate() in the optimized
non-surrogate loop, as the "first" (checked at the very beginning) might
be triggered by a non-surrogate-upper/lowercase char.

Thanks!
-Sherman