make audio driver selection exclusive
fix #20677: playing position is not displayed in fret diagram
fix #20678: Stems go crazy when converting note head to Note.HEAD_SLASH
Instrument dialogue: when a new staff is added and/or is linked to another staff

1) It is not completely initialized (not from dlg item settings anyway)

2) it is not inserted in the linked staff list.
Merge pull request #288 from mgavioli/INSTR_DLG_linked_staves_and_proper_staff_init

INSTR. DLG: new or newly linked staved not managed correctly
HARMONY and FIGURED_BASS editing shares the generic STATE_TEXT_EDIT. This causes shortcuts for HARMONY and FIG_BASS which are characters to be 'eaten' while editing other types of Text.

The branch adds a STATE_HARMONY_FIGBASS_EDIT, for actions specific to them, making any character used their shortcuts available while editing other types of textual elements.
Merge pull request #290 from mgavioli/STATE_HARMONY_FIGBASS_EDIT

Add a STATE_HARMONY_FIGBASS_EDIT state
End-Start-Repeat Bar line:

When at end of system, the From-To span of the separate Start bar line is not adjusted to staff From-To span
Merge pull request #289 from mgavioli/ENDSTARTREP_BARLINE_start_set_span

End-Start-Repeat Bar line: span of separate Start not always correct
gcc version check set to >= 4.7
Merge pull request #291 from heuchi/update_gcc_version_check

gcc version check set to >= 4.7
fix resource file for mac