Add STDP code generation for SpiNNaker target

[clinssen]

Replaces #1236.

NOTE: for now, manually remove the checks in /home/spinnaker/source/sPyNNaker/neural_modelling/makefiles/synapse_only/synapse_build.mk on lines 99-104:

diff --git a/neural_modelling/makefiles/synapse_only/synapse_build.mk b/neural_modelling/makefiles/synapse_only/synapse_build.mk
index b6bfaffa29..004250ecff 100644
--- a/neural_modelling/makefiles/synapse_only/synapse_build.mk
+++ b/neural_modelling/makefiles/synapse_only/synapse_build.mk
@@ -96,12 +96,6 @@ else
     ifneq ($(SYNAPSE_DYNAMICS), $(SYNAPSE_DYNAMICS_STATIC))
         STDP_ENABLED = 1
 
-        ifndef TIMING_DEPENDENCE_H
-            $(error TIMING_DEPENDENCE_H is not set which is required when SYNAPSE_DYNAMICS ($(SYNAPSE_DYNAMICS_C)) != $(SYNAPSE_DYNAMICS_STATIC))
-        endif
-        ifndef WEIGHT_DEPENDENCE_H
-            $(error WEIGHT_DEPENDENCE_H is not set which is required when SYNAPSE_DYNAMICS ($(SYNAPSE_DYNAMICS_C)) != $(SYNAPSE_DYNAMICS_STATIC))
-        endif
     endif
 endif
 
@@ -205,8 +199,10 @@ endif
 
 #STDP Build rules If and only if STDP used
 ifeq ($(STDP_ENABLED), 1)
-    STDP_INCLUDES:= -include $(WEIGHT_DEPENDENCE_H) -include $(TIMING_DEPENDENCE_H)
-    STDP_COMPILE = $(CC) -DLOG_LEVEL=$(PLASTIC_DEBUG) $(CFLAGS) -DSTDP_ENABLED=$(STDP_ENABLED) -DSYNGEN_ENABLED=$(SYNGEN_ENABLED) $(STDP_INCLUDES)

+    #STDP_INCLUDES:= -include $(WEIGHT_DEPENDENCE_H) -include $(TIMING_DEPENDENCE_H)
+    #STDP_INCLUDES:= -include $(WEIGHT_DEPENDENCE_H) -include $(TIMING_DEPENDENCE_H)
+    #STDP_COMPILE = $(CC) -DLOG_LEVEL=$(PLASTIC_DEBUG) $(CFLAGS) -DSTDP_ENABLED=$(STDP_ENABLED) -DSYNGEN_ENABLED=$(SYNGEN_ENABLED) $(STDP_INC
LUDES)
+    STDP_COMPILE = $(CC) -DLOG_LEVEL=$(PLASTIC_DEBUG) $(CFLAGS) -DSTDP_ENABLED=$(STDP_ENABLED) -DSYNGEN_ENABLED=$(SYNGEN_ENABLED)
 
     $(SYNAPSE_DYNAMICS_O): $(SYNAPSE_DYNAMICS_C)
        # SYNAPSE_DYNAMICS_O stdp