MDEV-712 - LP:1024239 - Mysqlclient exports the same symbols as openssl

Compile yassl and taocrypt using -fvisibility=hidden, when possible.  This prevent symbols from being exported.

configure.in

@@ -2513,6 +2513,18 @@ if test "x$mysql_cv_bss_start" = xyes; then
             [Define to 1 if compiler defines __bss_start.])
 fi
 
+# check for -fvisibility=hidden compiler support (GCC >= 4)
+saved_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -fvisibility=hidden -fvisibility-inlines-hidden"
+AC_MSG_CHECKING([if ${CXX} supports -fvisibility=hidden -fvisibility-inlines-hidden])
+AC_COMPILE_IFELSE([char foo;],
+      [ AC_MSG_RESULT([yes])
+        SYMBOL_VISIBILITY="-fvisibility=hidden" SYMBOL_VISIBILITY_INLINES="-fvisibility-inlines-hidden" ],
+        AC_MSG_RESULT([no]))
+CFLAGS="$saved_CFLAGS"
+AC_SUBST(SYMBOL_VISIBILITY)
+AC_SUBST(SYMBOL_VISIBILITY_INLINES)
+
 AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_CHECK_HEADERS(cxxabi.h)

extra/yassl/src/Makefile.am

@@ -5,4 +5,5 @@ libyassl_la_SOURCES = buffer.cpp cert_wrapper.cpp crypto_wrapper.cpp \
 	handshake.cpp lock.cpp log.cpp socket_wrapper.cpp ssl.cpp \
 	template_instnt.cpp timer.cpp yassl_imp.cpp yassl_error.cpp yassl_int.cpp
 EXTRA_DIST = $(wildcard ../include/*.hpp) $(wildcard ../include/openssl/*.h)
-AM_CXXFLAGS = -DYASSL_PURE_C -DYASSL_PREFIX @yassl_thread_cxxflags@
+AM_CXXFLAGS = -DYASSL_PURE_C -DYASSL_PREFIX @yassl_thread_cxxflags@ \
+	@SYMBOL_VISIBILITY@ @SYMBOL_VISIBILITY_INLINES@

extra/yassl/taocrypt/src/Makefile.am

@@ -9,6 +9,7 @@ libtaocrypt_la_SOURCES  = aes.cpp aestables.cpp algebra.cpp arc4.cpp \
         tftables.cpp twofish.cpp rabbit.cpp hc128.cpp
 
 libtaocrypt_la_CXXFLAGS = @yassl_taocrypt_extra_cxxflags@ -DYASSL_PURE_C \
-			  @yassl_thread_cxxflags@
-
+			  @yassl_thread_cxxflags@ \
+			  @SYMBOL_VISIBILITY@ @SYMBOL_VISIBILITY_INLINES@
+ 
 EXTRA_DIST = $(wildcard ../include/*.hpp)