Fix for Valgrind-reported jump/move dep on uninitialised values
Fix for Valgrind-reported jump/move dep on uninitialised values

A stack-allocated struct needs zeroing out before use.

> 5 errors in context 1 of 2:
> Conditional jump or move depends on uninitialised value(s)
>    at 0x5A031A7: psf_open_file (sndfile.c:2935)
>    by 0x4E8CBEF: csoundFileOpenWithType (envvar.c:1104)
>    by 0x50A80A8: filegrain_init (syncgrain.c:442)
>    by 0x4E9D4B6: init_pass (insert.c:117)
>    by 0x4E9EE8C: insert_event (insert.c:479)
>    by 0x4E9E0DF: insert (insert.c:305)
>    by 0x4EB0227: process_score_event (musmon.c:833)
>    by 0x4EB0D61: sensevents (musmon.c:1042)
>    by 0x4E83031: csoundPerform (csound.c:2255)
>    by 0x109928: main (csound_main.c:328)
>  Uninitialised value was created by a stack allocation
>    at 0x50A7D37: filegrain_init (syncgrain.c:404)

csound/csound,csound/csound,csound/csound,csound/csound,csound/csound,csound/csound,csound/csound,csound/csound,csound/csound,csound/csound