Disable K&R style function definitions for WARNS=6.

Unfortunately there are two slight problems with that:

- Yacc and lex might generate code that generates warnings because of
  this. Require yacc and lex to be rebuilt during bootstrap. I'm not
  incrementing __FreeBSD_version here, because I assume someone else
  will do this eventually.

- When running `make buildkernel', it uses share/mk from the source
  treeo to build aicasm. Because aicasm also depends on lex, this would
  break. Lower WARNS to 5 for now. We should just increment it to 6
  again somewhere in the very far future.

Makefile.inc1

@@ -940,6 +940,11 @@ _mklocale=	usr.bin/mklocale
 _sed=		usr.bin/sed
 .endif
 
+.if ${BOOTSTRAPPING} < 900006
+_lex=		usr.bin/lex
+_yacc=		usr.bin/yacc
+.endif
+
 .if ${BOOTSTRAPPING} < 700018
 _gensnmptree=	usr.sbin/bsnmpd/gensnmptree
 .endif
@@ -966,6 +971,8 @@ bootstrap-tools:
     ${_mklocale} \
     usr.bin/rpcgen \
     ${_sed} \
+    ${_lex} \
+    ${_yacc} \
     usr.bin/xinstall \
     ${_gensnmptree} \
     usr.sbin/config \

share/mk/bsd.sys.mk

@@ -47,7 +47,8 @@ CWARNFLAGS	+=	-Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch\
 .  endif
 # BDECFLAGS
 .  if ${WARNS} >= 6
-CWARNFLAGS	+=	-Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls
+CWARNFLAGS	+=	-Wchar-subscripts -Winline -Wnested-externs\
+			-Wredundant-decls -Wold-style-definition
 .  endif
 .  if ${WARNS} >= 2 && ${WARNS} <= 4
 # XXX Delete -Wuninitialized by default for now -- the compiler doesn't

sys/dev/aic7xxx/aicasm/Makefile

@@ -15,7 +15,7 @@ SRCS=	${GENHDRS} ${CSRCS} ${YSRCS} ${LSRCS}
 CLEANFILES+= ${GENHDRS} ${YSRCS:R:C/(.*)/\1.output/g}
 DPADD=	${LIBL}
 LDADD=	-ll
-WARNS?=	6
+WARNS?=	5
 
 # Correct path for kernel builds
 # Don't rely on the kernel's .depend file