ivlpp: Fixed include_path inconsistency

Discussions online and "standards" documents are never
conclusive, but the code that was present suggests that
iverilog adopts the sane practice of resolving relative
paths against the directory of the file that is currently
being processed.

Unfortunately, when a relative path is made absolute, the
code forgot to update the necessary include_stack_t object.

This has now been fixed.

Signed-off-by: Michael Witten <mfwitten@mit.edu>

ivlpp/lexor.lex

@@ -1195,6 +1195,7 @@ static void do_include()
 		  sprintf(path, "%s/%s", include_dir[idx], standby->path);
 		  standby->file = fopen(path, "r");
 		  if (standby->file) {
+			standby->path = strdup(path);
 			if(depend_file) {
 			    fprintf(depend_file, "%s\n", path);
 			}