use standard functions in pitch2xml instead of homegrown
add MusicMXL regression test script
add tablature testfile for B#, B##, Cb and Cbb
cleanup pitch2xml
cleanup pitch2xml
add testTablature3.xml  to tst_mxml_io.cpp
Merge pull request #603 from lvinken/23969-Cb-in-tab

23969 cb in tab