tests/arch_test is currently being used for two purposes:
- by vg_regtest for determining if a directory name matches an architecture;
- by various .vgtest files for detecting x86/AMD64 features.

This commit splits it in two for the two different purposes, which makes
things clearer.

Specific changes

- Moved the x86/AMD64 feature detection stuff out of arch_test.c, and
  into the new x86_amd64_feature.c.  Updated the relevant .vgtest files for
  the change.

- In vg_regtest, now a prereq command must return 0 (prereq satisfied) or 1
  (prereq not satisfied).  Anything else makes vg_regtest abort.  This
  makes obvious any problems with prereq tests rather than just making the
  tests skip innocuously.  (We previously had exactly such a problem on the
  DARWIN branch;  the x86 feature detection tests caused segfaults so the
  tests were incorrectly skipped.  This change will catch any similar future
  problem.)

- Changed os_test from a script to a C program, matching cpu_test.

- Removed some unintentional darwin stuff from platform_test.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@9316 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 70fefaf..f292f77 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -8,7 +8,6 @@
 	filter_numbers \
 	filter_stderr_basic \
 	filter_sink \
-	os_test \
 	platform_test \
 	vg_regtest
 
@@ -16,7 +15,9 @@
 
 check_PROGRAMS = \
 	arch_test \
-	true
+	os_test \
+	true \
+	x86_amd64_features
 
 AM_CFLAGS   += $(AM_FLAG_M3264_PRI)
 AM_CXXFLAGS += $(AM_FLAG_M3264_PRI)