ptrace supports threads

Fujitsu: POSTK_DEBUG_TEMP_FIX_53, POSTK_DEBUG_ARCH_DEP_44
Refs: #771, #1179, #1143
Change-Id: Ie17ece6864f0eeb0c0e550f4e369abb77980a0d0

test/issues/771+1179+1143/gdblist

@@ -0,0 +1,20 @@
+base a2-run
+base foll-fork
+base fork-detach
+threads atomic-seq-threaded
+threads bp_in_thread
+threads bt-clone-stop
+threads corethreads
+threads dlopen-libpthread
+threads fork-child-threads
+threads killed
+threads pthread_cond_wait
+threads switch-threads
+threads thread-specific
+threads thread_check
+threads thread_events
+threads threaded-exec
+threads threxit-hop-specific
+threads tls-nodebug
+threads tls-sepdebug
+threads tls-var