Support INSTALL_PREFIX for packagers.

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Reviewed by:
PR:
diff --git a/ssl/Makefile.ssl b/ssl/Makefile.ssl
index 53a3670..ab34611 100644
--- a/ssl/Makefile.ssl
+++ b/ssl/Makefile.ssl
@@ -7,6 +7,8 @@
 CC=	cc
 INCLUDES= -I../crypto -I../include
 CFLAG=-g
+INSTALL_PREFIX=
+OPENSSLDIR=     /usr/local/ssl
 INSTALLTOP=/usr/local/ssl
 MAKE=		make -f Makefile.ssl
 MAKEDEPEND=	$(TOP)/util/domd $(TOP)
@@ -68,8 +70,8 @@
 install:
 	@for i in $(EXHEADER) ; \
 	do  \
-	(cp $$i $(INSTALLTOP)/include/openssl/$$i; \
-	chmod 644 $(INSTALLTOP)/include/openssl/$$i ); \
+	(cp $$i $(INSTALL_PREFIX)$(INSTALLTOP)/include/openssl/$$i; \
+	chmod 644 $(INSTALL_PREFIX)$(INSTALLTOP)/include/openssl/$$i ); \
 	done;
 
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