Use underscores instead of hyphens

This matches the things around it better.

Author: Owen

src/ansi-c/expr2c.cpp

@@ -3427,7 +3427,7 @@ std::string expr2ct::convert_with_precedence(
     return convert_function(src, "W_OK", precedence = 16);
 
   else if(src.id() == ID_is_invalid_pointer)
-    return convert_function(src, "IS-INVALID-POINTER", precedence = 16);
+    return convert_function(src, "IS_INVALID_POINTER", precedence = 16);
 
   else if(src.id()==ID_good_pointer)
     return convert_function(src, "GOOD_POINTER", precedence=16);

src/util/irep_ids.def

@@ -217,7 +217,7 @@ IREP_ID_ONE(invalid)
 IREP_ID_TWO(C_invalid_object, #invalid_object)
 IREP_ID_ONE(pointer_offset)
 IREP_ID_ONE(pointer_object)
-IREP_ID_TWO(is_invalid_pointer, is-invalid-pointer)
+IREP_ID_ONE(is_invalid_pointer)
 IREP_ID_ONE(ieee_float_equal)
 IREP_ID_ONE(ieee_float_notequal)
 IREP_ID_ONE(isnan)