Fix for various Valgrind-reported memory leaks
Fix for various Valgrind-reported memory leaks

Several functions in csound_debugger_test.c fail to call
csoundDestroyMessageBuffer().

Typical example:

> 40 bytes in 1 blocks are indirectly lost in loss record 98 of 244
>    at 0x4C2FDAF: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
>    by 0x5248F64: csoundCreateMutex (threads.c:478)
>    by 0x50964B9: csoundCreateMessageBuffer (csound.c:4240)
>    by 0x109286: test_debugger_init (csound_debugger_test.c:27)
>    by 0x4E40D36: run_single_test.constprop.5 (TestRun.c:991)
>    by 0x4E4106F: run_single_suite.constprop.4 (TestRun.c:876)
>    by 0x4E413BD: CU_run_all_tests (TestRun.c:367)
>    by 0x10AE33: main (csound_debugger_test.c:547)

ketchupok/csound,csound/csound,csound/csound,csound/csound,csound/csound,ketchupok/csound,ketchupok/csound,csound/csound,csound/csound,ketchupok/csound,ketchupok/csound,ketchupok/csound,ketchupok/csound,ketchupok/csound,ketchupok/csound,ketchupok/csound,csound/csound,csound/csound,csound/csound,csound/csound