Function PROPER: Don't use a regular expression syntax that is not available on Andro...

Function PROPER: Don't use a regular expression syntax that is not available on Android. Actually the use of regular expression in this case was overkill, slow and even incorrect in corner cases, the function can be done without regex easily and runs a bit faster anyway (microBench is down from 4sec to 2s)
Also added a unit-test to ensure the behavior stays the same (except in cases where it needed fixing, e.g. some toUppercase() leads to more than one character which was handled incorrectly)

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1752779 13f79535-47bb-0310-9956-ffa450edef68