Add ability to use a statically generated ecmult context.

This vastly shrinks the size of the context required for signing on devices with
memory-mapped Flash.

Tables are generated by the new gen_context tool into a header.

Makefile.am

@@ -74,4 +74,22 @@ tests_LDFLAGS = -static
 TESTS = tests
 endif
 
+if USE_ECMULT_STATIC_PRECOMPUTATION
+CPPFLAGS_FOR_BUILD +=-I.
+CFLAGS_FOR_BUILD += -Wall -Wextra -Wno-unused-function
+
+gen_context_OBJECTS = gen_context.o
+
+gen_%.o: src/gen_%.c
+	$(CC_FOR_BUILD) $(CPPFLAGS_FOR_BUILD) $(CFLAGS_FOR_BUILD) -c $< -o $@
+
+gen_context$(BUILD_EXEEXT): $(gen_context_OBJECTS)
+	$(CC_FOR_BUILD) $^ -o $@
+
+BUILT_SOURCES = src/ecmult_static_context.h
+
+src/ecmult_static_context.h: gen_context
+	./gen_context
+endif
+
 EXTRA_DIST = autogen.sh