Add option to set csound6 textdomain

Can be defined in Custom.cmake.
When not defined and on linux, automatically set it.
check for USE_DOUBLE in perf thread
bit more on score language
preparing scope tester
fix to expseg
further fixes to a-rate envelopes
merge fix
trying to get scope to work and failing
Merge branch 'develop' of github.com:csound/csound into develop
reorganise score parser tests
more reorganise score parser tests
restore incorrectly deleted lines
fix keyboard failure
now builds score parser
Pulseaudio rt module fixes

Buffer size must take into account the number of channels
Input number of channels is different from output number of channels
In record, write the correct number of bytes (float != MYFLT)
broken SCORE_PARSER
Merge branch 'develop' of github.com:csound/csound into develop
broken SCORE_PARSER
added missing semicolon
add -DSCORE_PARSER only to libcsound target