cleanup some partially broken patches

- tests/Makefile:
  fix commit de54586d5b
  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 c52d79605a 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 5280293d6b
  Do not build tcc.o with -DONE_SOURCE because we finally build tcc
  from tcc.o and libtcc.a/so

tests/Makefile

@@ -3,10 +3,10 @@
 #
 
 # what tests to run
-TESTS = libtest test1 test3
+TESTS = libtest test3
 
 # these should work too
-TESTS += test2 speedtest btest weaktest
+# TESTS += test1 test2 speedtest btest weaktest
 
 # these don't work as they should
 # TESTS += test4 asmtest