Port build to gcc -fcheck-pointer-bounds

This does not let Emacs run, just build.
* lib-src/etags.c (main):
* lib-src/profile.c (main):
Use return, not exit.
* src/bytecode.c (BYTE_CODE_THREADED) [__CHKP__]:
Do not define, as -fcheck-pointer-bounds is incompatible with taking
addresses of labels.
* src/menu.c (Fx_popup_dialog): Use eassume, not eassert,
to pacify gcc -fcheck-pointer-bounds -Wnull-dereference.

lib-src/etags.c

@@ -1330,7 +1330,7 @@ main (int argc, char **argv)
 	    pfatal (tagfile);
 	}
 
-      exit (EXIT_SUCCESS);
+      return EXIT_SUCCESS;
     }
 
   /* From here on, we are in (CTAGS && !cxref_style) */
@@ -1383,7 +1383,7 @@ main (int argc, char **argv)
 	z = stpcpy (z, tagfile);
 	*z++ = ' ';
 	strcpy (z, tagfile);
-	exit (system (cmd));
+	return system (cmd);
       }
   return EXIT_SUCCESS;
 }

lib-src/profile.c

@@ -85,13 +85,13 @@ main (void)
 	  puts (get_time ());
 	  break;
 	case 'q':
-	  exit (EXIT_SUCCESS);
+	  return EXIT_SUCCESS;
 	}
       /* Anything remaining on the line is ignored.  */
       while (c != '\n' && c != EOF)
 	c = getchar ();
     }
-  exit (EXIT_FAILURE);
+  return EXIT_FAILURE;
 }