Add cgo2c program to translate mixed Go/C code into C. This

lets us use a single source file for both 6c and gcc, handling
the incompatible handling of return values.

R=rsc
DELTA=649  (613 added, 35 deleted, 1 changed)
OCL=22682
CL=22730

Author: ianlancetaylor

src/runtime/Makefile

@@ -24,6 +24,7 @@ LIBOFILES=\
 	array.$O\
 	mem.$O\
 	malloc.$O\
+	malloc_go.$O\
 	mcache.$O\
 	mcentral.$O\
 	mfixalloc.$O\
@@ -57,14 +58,21 @@ nuke:
 	rm -f *.$(O) *.a $(GOROOT)/lib/$(LIB)
 
 clean:
-	rm -f *.$(O) *.a runtime.acid
+	rm -f *.$(O) *.a runtime.acid cgo2c
 
 %.$O:	%.c
 	$(CC) -wF $<
 
 sys_file.$O:	sys_file.c sys_types.h $(OS_H)
 	$(CC) -wF -D$(GOARCH)_$(GOOS) $<
 
+cgo2c: cgo2c.c
+	quietgcc -o $@ $<
+
+%.c:	%.cgo cgo2c
+	./cgo2c < $< > $@.tmp
+	mv -f $@.tmp $@
+
 %.$O:	%.s
 	$(AS) $<