Improvements to SMPTE and MIDIDriverWin32

Added methods to SMPTE class to convert directly from/to SMPTE and
milliseconds.
Now MIDIDriverWin32 sends also sysex messages. This is tested by file
songs\test_sysex.mid which sends a GM reset message. THIS IS THE ONLY
TEST I COULD DO! Needs more testing
Added other documentation

doxygen comments to files file.h fileread.h filrewrite.h