Put defs into a generated file.

This is only part of the solution, we still need to update joy.h and
KEYWORDS.txt when defs.txt changes, and we need to handle names that
have non-C-identifier characters in them.

But it's a start...

implementations/C/Makefile

@@ -1,4 +1,4 @@
-OBJS=joy.o keywords.o
+OBJS=joy.o keywords.o definitions.o
 
 # On FreeBSD gc and gmp are installed in /usr/local/:
 STATIC_GCLIB=/usr/local/lib/libgc.a /usr/local/lib/libgmp.a
@@ -17,6 +17,9 @@ joy: ${OBJS} $(STATIC_GCLIB)
 
 joy.o: joy.h
 
+definitions.c: defs.txt convert_defs.py
+	python convert_defs.py > definitions.c
+
 
 # Gperf doesn't add anything to '{""}' unused entries in the wordlist.
 # This causes "warning: missing field 'func' initializer [-Wmissing-field-initializers]"