fix sys:get_state/1,2 and sys:replace_state/2,3 when sys suspended

Add two new system callbacks Module:system_get_state/1 and
Module:system_replace_state/2 to allow sys:get_state/1,2 and
sys:replace_state/2,3 to operate correctly even if a process is sys
suspended. Modify gen_server, gen_fsm, and gen_event to support the new
callbacks.

If a callback module does not export these functions, then by default the
Misc value (the same as that passed as the final argument to
sys:handle_system_msg/6, and returned as part of the return value of
sys:get_status/1,2) is treated as the callback module's state.

The previous behaviour of intercepting the system message and passing a
tuple of size 2 as the last argument to sys:handle_system_msg/6 is no
longer supported.

Add tests to verify the correctness of sys:get_state/1,2 and
sys:replace_state/2,3 when processes are sys suspended. Add two tests for
modules that implement special processes, one that exports
system_get_state/1 and system_replace_state/2 and one that doesn't.

Much of the credit for this patch goes to James Fish, who reported the
initial problem and implemented much of the fix.

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/stdlib/test/Makefile b/lib/stdlib/test/Makefile
index af82f22b21..39f6ce423a 100644
--- a/lib/stdlib/test/Makefile
+++ b/lib/stdlib/test/Makefile
@@ -73,6 +73,8 @@ MODULES= \
 	supervisor_SUITE \
 	supervisor_bridge_SUITE \
 	sys_SUITE \
+	sys_sp1 \
+	sys_sp2 \
 	tar_SUITE \
 	timer_SUITE \
 	timer_simple_SUITE \