Cleanup of VAX and VMS code, from Pat Rankin:

Cleanup of VAX and VMS code, from Pat Rankin:
* config/obj-vms.c: Changed exported function names to lower case.  (Changed
call sites in write.c.)  Declare VMS system function names used, conditional on
actually being on VMS.  Changed many functions that returned no useful value to
now be declared to return void.  Removed many unused variables.  Supply missing
return statements or values.  Supply `default' case in switch statements.
Ensure local variables get initialized.
* config/tc-vax.c: Minor changes to silence "gcc -Wall".
* config/obj-vms.h, config/tc-vax.h: Added some missing declarations.