Fix realloc() bug in gr65

The pointer to the input buffer was not being updated after a call to
realloc(), causing the program to crash if realloc() moved the buffer.

src/grc65/main.c

@@ -861,7 +861,7 @@ static char *filterInput (FILE *F, char *tbl)
         }
         if (a == EOF) {
             tbl[i] = '\0';
-            xrealloc (tbl, i + 1);
+            tbl = xrealloc (tbl, i + 1);
             break;
         }
         if (IsSpace (a)) {