Fix #814: raise on div-0, add inf isinf nan isnan

compile.c

@@ -2,6 +2,7 @@
 #define _GNU_SOURCE // for strdup
 #endif
 #include <assert.h>
+#include <math.h>
 #include <string.h>
 #include <stdlib.h>
 #include "compile.h"
@@ -161,6 +162,12 @@ int block_is_const(block b) {
   return (block_is_single(b) && b.first->op == LOADK);
 }
 
+int block_is_const_inf(block b) {
+  return (block_is_single(b) && b.first->op == LOADK &&
+          jv_get_kind(b.first->imm.constant) == JV_KIND_NUMBER &&
+          isinf(jv_number_value(b.first->imm.constant)));
+}
+
 jv_kind block_const_kind(block b) {
   assert(block_is_const(b));
   return jv_get_kind(b.first->imm.constant);