VVP cleanup of ',' at end of enum and missing extern "C"

This patch is similar to the previous patches and cleans up a single
place in the vvp directory where an enum had a trailing ',' and a
place where a C++ routine needed extern "C".

vvp/compile.cc

@@ -67,7 +67,7 @@ enum operand_e {
 	/* The operand is a second functor pointer */
       OA_FUNC_PTR2,
 	/* The operand is a VPI handle */
-      OA_VPI_PTR,
+      OA_VPI_PTR
 };
 
 struct opcode_table_s {

vvp/schedule.cc

@@ -519,7 +519,7 @@ bool schedule_stopped(void)
  * These are the signal handling infrastructure. The SIGINT signal
  * leads to an implicit $stop.
  */
-static void signals_handler(int)
+extern "C" void signals_handler(int)
 {
       schedule_stopped_flag = true;
 }