Makefile: don't define -Werror for ccanlint.

It's useful for developers, but not so much for casual users.  For example,
RHEL 5.6 has qsort_r, but no prototype, which causes a warning.

Makefile-ccan

@@ -4,7 +4,7 @@
 
 #CCAN_CFLAGS=-g -O3 -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations
 CCAN_CFLAGS=-g -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wwrite-strings -DCCAN_STR_DEBUG=1
-CFLAGS = $(CCAN_CFLAGS) -I. $(DEPGEN) -Werror
+CFLAGS = $(CCAN_CFLAGS) -I. $(DEPGEN)
 
 
 default: libccan.a