tests: run tests for each supported personality

When strace supports more than one personality, run test suite
for each personality supported by the host system.

* bootstrap: Create tests-m32 and tests-mx32 subtrees from tests.
* configure.ac: Check for -m32 and -mx32 runtime support.
(AC_CONFIG_FILES): Add tests-m32/Makefile and tests-mx32/Makefile.
* Makefile.am [HAVE_M32_RUNTIME] (TESTS_M32): Define.
[HAVE_MX32_RUNTIME] (TESTS_MX32): Define.
(SUBDIRS): Add $(TESTS_M32) $(TESTS_MX32).
* .gitignore: Add /tests-m32 and /tests-mx32.
diff --git a/Makefile.am b/Makefile.am
index 83eef2e..a00aad2 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,6 +1,12 @@
 # Automake input for strace.
 
-SUBDIRS = tests
+if HAVE_M32_RUNTIME
+TESTS_M32 = tests-m32
+endif
+if HAVE_MX32_RUNTIME
+TESTS_MX32 = tests-mx32
+endif
+SUBDIRS = tests $(TESTS_M32) $(TESTS_MX32)
 
 bin_PROGRAMS = strace
 man_MANS = strace.1