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-pistachio/lib/mk/base-pistachio-common.mk

@@ -9,7 +9,6 @@ include $(BASE_DIR)/lib/mk/base-common.inc
 LIBS += startup-pistachio syscall-pistachio
 
 SRC_CC += capability.cc capability_raw.cc
-SRC_CC += signal_submit.cc
 SRC_CC += rpc_dispatch_loop.cc
 SRC_CC += thread.cc thread_bootstrap.cc thread_myself.cc
 

repos/base-pistachio/lib/mk/base-pistachio.mk

@@ -5,3 +5,5 @@ LIBS   += base-pistachio-common syscall-pistachio cxx timeout
 SRC_CC += thread_start.cc
 SRC_CC += cache.cc
 SRC_CC += capability_space.cc
+SRC_CC += signal_transmitter.cc
+SRC_CC += signal.cc

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

@@ -36,6 +36,8 @@ SRC_CC       = stack_area.cc \
                region_map_support.cc \
                rom_session_component.cc \
                signal_source_component.cc \
+               signal_transmitter_proxy.cc \
+               signal_receiver.cc \
                thread_start.cc \
                trace_session_component.cc
 
@@ -59,6 +61,8 @@ vpath capability_space.cc         $(GEN_CORE_DIR)
 vpath io_mem_session_component.cc $(GEN_CORE_DIR)
 vpath io_mem_session_support.cc   $(GEN_CORE_DIR)
 vpath signal_source_component.cc  $(GEN_CORE_DIR)
+vpath signal_transmitter_proxy.cc $(GEN_CORE_DIR)
+vpath signal_receiver.cc          $(GEN_CORE_DIR)
 vpath trace_session_component.cc  $(GEN_CORE_DIR)
 vpath dataspace_component.cc      $(GEN_CORE_DIR)
 vpath dump_alloc.cc               $(GEN_CORE_DIR)