stuff & fixes

libtcc.c:
- revert "Small patch to allow..." (someone's personal easteregg)
  (see da3a763e97)
- check return value from macho_load_tbd/dylib

tcc.c:
- remove help for "not yet implemented" option

tccelf.c:
- check PIE's for "unresolved symbols"

tccgen.c:
- avoid int->double->int cast
  (see a46372e910)
- fix constant propagation with pseudo long doubles
  (must mask out VT_LONG from type)
- cleanup find_field() (again)

tccpp.c:
- disallow strings and double constants in #if expressions

win32/include/uchar.h:
- change file mode

tests/libtcc_test_mt.c

@@ -209,9 +209,8 @@ TF_TYPE(thread_test_complex, vn)
     sleep_ms(2);
     ret = tcc_add_file(s, argv[0]);
     sleep_ms(3);
-    if (ret < 0)
-        exit(1);
-    tcc_run(s, argc, argv);
+    if (ret == 0)
+        tcc_run(s, argc, argv);
     tcc_delete(s);
     fflush(stdout);
     return 0;