Remove the CFLAGS+=-I${CURDIR}/net that I previously added.

Since Bruce changed the #include <res_config.h> to #include "res_config.h"
this is no longer needed, and only makes the 'make' more verbose for
no real reason.

lib/libc/net/Makefile.inc

@@ -3,7 +3,6 @@
 # machine-independent net sources
 .PATH: ${.CURDIR}/${MACHINE}/net ${.CURDIR}/net
 
-CFLAGS+= -I${.CURDIR}/net
 SRCS+=	gethostbydns.c gethostbyht.c gethostbynis.c gethostnamadr.c \
 	getnetbydns.c getnetbyht.c getnetbynis.c getnetnamadr.c \
 	getproto.c getprotoent.c getprotoname.c getservbyname.c \