Remove unused code. No functional change intended.

- We don't need to define __NetBSD__, C compilers do this for us.
- Defines which don't appear anywhere in src
- Don't need libpthread/librt

external/bsd/acpica/bin/iasl/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.19 2018/05/31 09:08:25 mrg Exp $
+# $NetBSD: Makefile,v 1.20 2018/06/27 16:13:43 maya Exp $
 
 .if (${MACHINE_ARCH} == "i386" || ${MACHINE_ARCH} == "x86_64")
 PROG=	iasl
@@ -11,13 +11,12 @@ TOPDIR=	${NETBSDSRCDIR}/sys/external/bsd/acpica/dist/compiler
 .include <bsd.own.mk>
 
 CPPFLAGS+=	-I${TOPDIR}/../include -I${TOPDIR} -I.
-CPPFLAGS+=	-D__NetBSD__ -DACPI_ASL_COMPILER -DACPI_USE_ALTERNATE_TIMEOUT
-CPPFLAGS+=	-D_USE_BERKELEY_YACC
+CPPFLAGS+=	-DACPI_ASL_COMPILER -DACPI_USE_ALTERNATE_TIMEOUT
 .if ${MKREPRO:Uno} == "yes"
 CPPFLAGS+=	-DACPI_REPRO
 .endif
-LDADD+=		-ll -ly -lrt -lpthread
-DPADD+=		${LIBL} ${LIBY} ${LIBRT} ${LIBPTHREAD}
+LDADD+=		-ll -ly
+DPADD+=		${LIBL} ${LIBY}
 
 DPSRCS= aslcompilerparse.y aslcompilerlex.c aslcompilerparse.c \
 	dtparserparse.c dtparserlex.c prparserparse.c prparserlex.c