cleanup some partially broken patches

cleanup some partially broken patches

- tests/Makefile:
  fix commit de54586d5b45800e26952ec77b4f51ad4c1e0079
  This hunk it unrelated to the other changes (which are about MacOSX).
  It is not useful and partially wrong.  Optional tests are meant to
  stay optional, btest would work only for i386

- tcc.h:
  fix commit c52d79605a3c895a16e18f0b7193f1f4b480a60f by unknown
  The message says it's for MINTW but the patch has obviously
  no effect for MINGW (which defines __GNUC__).  However the patch
  seems useful for MSC which however needs _strto(u)i64 with underscore.

- Makefile:
  fix commit 5280293d6b16bbe24dfda76e37f32322fa2874ca
  Do not build tcc.o with -DONE_SOURCE because we finally build tcc
  from tcc.o and libtcc.a/so