[m-rev.] diff: Support threads on AIX.

[Peter Wang]

configure.ac:
    Set flags to build Boehm GC with threads support and parallel
    marking on AIX.

    Delete commented out code for HPUX.

diff --git a/configure.ac b/configure.ac
index 3ca4a4b95..71fa15fd9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3255,11 +3255,13 @@ case "$host" in
         avoid_sbrk=yes
         ;;
 
-### # The threads stuff on HPUX is not yet enabled because
-### # we don't have an HPUX box to test it on.
-### *hpux*)
-###     CFLAGS_FOR_THREADS="" # XXX incomplete
-###     THREAD_LIBS="-lpthread -lrt" ;;
+    *-aix*)
+        CFLAGS_FOR_THREADS="-DGC_THREADS -D_REENTRANT"
+        THREAD_LIBS="-lpthread"
+        ENABLE_BOEHM_THREAD_LOCAL_ALLOC="-DTHREAD_LOCAL_ALLOC"
+        ENABLE_BOEHM_PARALLEL_MARK="-DPARALLEL_MARK"
+        avoid_sbrk=yes  # assumed
+        ;;
 
     *)
         # Multithreading not (yet) supported on other architectures.
-- 
2.21.0