Allow awk (the one true one!) to handle 64 files instead of just 20.

The current FreeBSD syscall generation script uses all 20 and I need
another open file.

It's a shame that something named as the 'one-true-awk' is so limited
by an old denition like FOPEN_MAX when it could just make the file
handling dynamic.

This is done to avoid touching contrib sources on a vendor branch.

usr.bin/awk/Makefile

@@ -6,7 +6,7 @@ AWKSRC=	${.CURDIR}/../../contrib/one-true-awk
 PROG=	awk
 SRCS=	awkgram.y b.c lex.c lib.c main.c parse.c proctab.c run.c tran.c ytab.h
 
-CFLAGS+= -DHAS_ISBLANK -I. -I${AWKSRC}
+CFLAGS+= -DHAS_ISBLANK -I. -I${AWKSRC} -DFOPEN_MAX=64
 
 DPADD=	${LIBM}
 LDADD=	-lm