Add warnings to <regexp.h> and <sys/timeb.h>.

These header files only provide functionality that can be used in
combination with libcompat. In order to prevent people from including
them without any actual use (which happens a lot with <sys/timeb.h>),
put a warning here to make people more aware.

This means we have to lower WARNS for libcompat, which is no big deal.

include/regexp.h

@@ -37,6 +37,10 @@
 #ifndef	_REGEXP_H_
 #define	_REGEXP_H_
 
+#ifdef __GNUC__
+#warning "this file includes <regexp.h> which is deprecated, use <regex.h> instead"
+#endif
+
 /*
  * Definitions etc. for regexp(3) routines.
  *

lib/libcompat/Makefile

@@ -5,7 +5,7 @@ LIB=compat
 CFLAGS+=-DLIBC_SCCS -DSYSLIBC_SCCS -I${.CURDIR}/../libc/locale
 NO_PIC=
 
-WARNS?=	1
+WARNS?=	0
 
 .PATH:	${.CURDIR}/4.1/${MACHINE_ARCH} ${.CURDIR}/4.1 \
 	${.CURDIR}/4.3/${MACHINE_ARCH} ${.CURDIR}/4.3 \

sys/sys/timeb.h

@@ -38,6 +38,10 @@
 #ifndef _SYS_TIMEB_H_
 #define _SYS_TIMEB_H_
 
+#ifdef __GNUC__
+#warning "this file includes <sys/timeb.h> which is deprecated"
+#endif
+
 #include <sys/_types.h>
 
 #ifndef _TIME_T_DECLARED