Various minor fixes

* Re-add missing line in ISim invocation

* Fix documentation for Digilent mode (thanks, @keesj)

* Fix iMPACT invocation (thanks, @acid-maker)

Closes #1

Makefile

@@ -146,9 +146,8 @@ build/isim_%$(EXE): build/$(PROJECT)_sim.prj $(VSOURCE) $(VHDSOURCE) $(VTEST) $(
 	    -o isim_$*$(EXE) \
 	    work.$* work.glbl
 
-#FIXME TB ?= $(error Must set TB to name of a testbench module)
-
 isim: build/isim_$(TB)$(EXE)
+	@grep --no-filename --no-messages 'ISIM:' $(TB).{v,vhd} | cut -d: -f2 > build/isim_$(TB).cmd
 	@echo "run all" >> build/isim_$(TB).cmd
 	cd build ; ./isim_$(TB)$(EXE) -tclbatch isim_$(TB).cmd
 
@@ -164,7 +163,7 @@ isimgui: build/isim_$(TB)$(EXE)
 
 ifeq ($(PROGRAMMER), impact)
 prog: $(BITFILE)
-	$(XILINX)/impact -batch $(IMPACT_OPTS)
+	$(XILINX)/bin/$(XILINX_PLATFORM)/impact $(IMPACT_OPTS)
 endif
 
 ifeq ($(PROGRAMMER), digilent)

README.md

@@ -116,7 +116,7 @@ A number of other keys can be set in the project configuration, including:
             program -p 1
             quit
 
-      * `djtg`
+      * `digilent`
 
         Uses the Digilent JTAG utility for programming, which must be installed
         separately. The name of the board must be set as `DJTG_DEVICE`; the