base: restructure signal-submit initialization

This patch allows core's 'Signal_transmitter' implementation to sidestep
the 'Env::Pd' interface and thereby adhere to a stricter layering within
core. The 'Signal_transmitter' now uses - on kernels that depend on it -
a dedicated (and fairly freestanding) RPC proxy mechanism for signal
deliver, instead of channeling signals through the 'Pd_session::submit'
RPC function.

repos/base-nova/lib/mk/base-nova-common.mk

@@ -8,8 +8,8 @@ include $(BASE_DIR)/lib/mk/base-common.inc
 
 LIBS += startup-nova
 
-SRC_CC += signal_submit.cc
 SRC_CC += thread.cc thread_myself.cc
 SRC_CC += stack.cc
 SRC_CC += cap_map.cc
 SRC_CC += capability.cc
+SRC_CC += signal_transmitter.cc

repos/base-nova/lib/mk/base-nova.mk

@@ -3,3 +3,4 @@ include $(BASE_DIR)/lib/mk/base.inc
 LIBS   += base-nova-common cxx timeout
 SRC_CC += thread_start.cc
 SRC_CC += cache.cc
+SRC_CC += signal.cc

repos/base-nova/lib/mk/core-nova.inc

@@ -39,7 +39,9 @@ SRC_CC      += stack_area.cc \
                rom_session_component.cc \
                thread_start.cc \
                bios_data_area.cc \
-               trace_session_component.cc
+               trace_session_component.cc \
+               signal_transmitter_noinit.cc \
+               signal_receiver.cc
 
 INC_DIR      = $(REP_DIR)/src/core/include \
                $(REP_DIR)/src/include \
@@ -58,6 +60,8 @@ vpath pd_session_component.cc      $(GEN_CORE_DIR)
 vpath pd_upgrade_ram_quota.cc      $(GEN_CORE_DIR)
 vpath region_map_component.cc      $(GEN_CORE_DIR)
 vpath trace_session_component.cc   $(GEN_CORE_DIR)
+vpath signal_transmitter_noinit.cc $(GEN_CORE_DIR)
+vpath signal_receiver.cc           $(GEN_CORE_DIR)
 vpath io_port_session_component.cc $(GEN_CORE_DIR)/spec/x86
 vpath io_port_session_support.cc   $(GEN_CORE_DIR)/spec/x86
 vpath io_mem_session_component.cc  $(GEN_CORE_DIR)

repos/base-nova/src/lib/base/signal_transmitter.cc

@@ -11,18 +11,23 @@
  * under the terms of the GNU Affero General Public License version 3.
  */
 
-
 /* Genode includes */
 #include <base/signal.h>
 #include <base/log.h>
 #include <base/trace/events.h>
 
+/* base-internal includes */
+#include <base/internal/globals.h>
+
 /* NOVA includes */
 #include <nova/syscalls.h>
 
 using namespace Genode;
 
 
+void Genode::init_signal_transmitter(Env &) { }
+
+
 void Signal_transmitter::submit(unsigned cnt)
 {
 	{