Don't export BN_ (cryptlib BigNum functions) from libsbbs.so

Attempt to fix issue #680

This probably will need some llvm or other exceptional handling for
non GNU build systems.

src/sbbs3/GNUmakefile

@@ -161,7 +161,7 @@ $(SBBSMONO): $(MONO_OBJS) $(OBJS)
 # Synchronet BBS library Link Rule
 $(SBBS): $(JS_DEPS) $(CRYPT_DEPS) $(OBJS) $(LIBS) $(EXTRA_SBBS_DEPENDS) $(ENCODE_LIB) $(HASH_LIB) | $(LIBODIR)
 	@echo Linking $@
-	$(QUIET)$(MKSHPPLIB) $(LDFLAGS) -o $@ $(OBJS) $(SBBS_LIBS) $(SMBLIB_LIBS) $(LIBS) $(SHLIBOPTS) $(JS_LIBS) $(CRYPT_LIBS) $(ENCODE_LIBS) $(HASH_LIBS) $(XPDEV-MT_LIBS) $(FILE_LIBS)
+	$(QUIET)$(MKSHPPLIB) $(LDFLAGS) -o $@ $(OBJS) $(SBBS_LIBS) $(SMBLIB_LIBS) $(LIBS) $(SHLIBOPTS) $(JS_LIBS) $(CRYPT_LIBS) $(ENCODE_LIBS) $(HASH_LIBS) $(XPDEV-MT_LIBS) $(FILE_LIBS) -Wl,--version-script=sbbs.version
 
 # FTP Server Link Rule
 $(FTPSRVR): $(MTOBJODIR)/ftpsrvr.o

src/sbbs3/sbbs.version

+SBBS {
+	local: BN_*;  # hide cryptlib BigNum functions, prevent collision with OpenSSL
+};
+