Don't rely on default locale when using toUpperCase() and toLowerCase()

Don't rely on default locale when using toUpperCase() and toLowerCase()

Otherwise these methods may produce unexpected results if used for
strings that are intended to be interpreted locale independently.
Examples are programming language identifiers, protocol keys, and HTML
tags. For instance, "TITLE".toLowerCase() in a Turkish locale returns
"t\u0131tle", where '\u0131' is the LATIN SMALL LETTER DOTLESS I
character.

See
https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#toLowerCase--
http://blog.thetaphi.de/2012/07/default-locales-default-charsets-and.html

Bug: 511238
Change-Id: Id8d8f37d84d62239c918b81f8d883ed798d87656
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>