Enable compiling the X Server and modules with hidden symbols by default.

Note that it checks if support for symbol visibility is available by
the compiler, not if it is functional. It may have problems on non x86
architectures.
  To disable the feature, just pass the option "--disable-visibility"
to the X Server configure script.
  Unless using an alternate build schema, drivers built from a git
checkout will use the same "visibility" related CFLAGS used to compile
the X Server.

configure.ac

@@ -504,6 +504,9 @@ AC_ARG_ENABLE(builtin-fonts,  AS_HELP_STRING([--enable-builtin-fonts], [Use only
 AC_ARG_ENABLE(null-root-cursor, AS_HELP_STRING([--enable-null-root-cursor], [Use an empty root cursor (default: use core cursor)]),
                                  [NULL_ROOT_CURSOR=$enableval],
                                  [NULL_ROOT_CURSOR=no])
+AC_ARG_ENABLE(visibility,     AC_HELP_STRING([--enable-visibility], [Enable symbol visibility (default: auto)]),
+				[SYMBOL_VISIBILITY=$enableval],
+				[SYMBOL_VISIBILITY=auto])
 
 dnl GLX build options
 AC_ARG_WITH(mesa-source,     AS_HELP_STRING([--with-mesa-source=MESA_SOURCE], [Path to Mesa source tree]),
@@ -1229,6 +1232,46 @@ if test "x$XORG" = xyes; then
 	XORG_CFLAGS="$XORGSERVER_CFLAGS -DHAVE_XORG_CONFIG_H"
 	XORG_LIBS="$COMPOSITE_LIB $FIXES_LIB $XEXTXORG_LIB $GLX_LIBS $RANDR_LIB $RENDER_LIB $DAMAGE_LIB $MIEXT_DAMAGE_LIB $MIEXT_SHADOW_LIB $XI_LIB $XKB_LIB $SELINUX_LIB"
 
+	dnl ==================================================================
+	dnl symbol visibility
+	symbol_visibility=
+	have_visibility=disabled
+	if test x$SYMBOL_VISIBILITY != xno; then
+	    AC_MSG_CHECKING(for symbol visibility support)
+	    if test x$GCC = xyes; then
+		VISIBILITY_CFLAGS="-fvisibility=hidden"
+	    else
+		AC_CHECK_DECL([__SUNPRO_C], [SUNCC="yes"], [SUNCC="no"])
+		if test x$SUNCC = xyes; then
+		    VISIBILITY_CFLAGS="-xldscope=hidden"
+		else
+		    have_visibility=no
+		fi
+	    fi
+	    if test x$have_visibility != xno; then
+		save_CFLAGS="$CFLAGS"
+		CFLAGS="$CFLAGS $VISIBILITY_CFLAGS"
+		AC_TRY_COMPILE(
+		    [#include <X11/Xfuncproto.h>
+		     extern _X_HIDDEN int hidden_int;
+		     extern _X_EXPORT int public_int;
+		     extern _X_HIDDEN int hidden_int_func(void);
+		     extern _X_EXPORT int public_int_func(void);],
+		    [],
+		    have_visibility=yes,
+		    have_visibility=no)
+		CFLAGS=$save_CFLAGS
+	    fi
+	    AC_MSG_RESULT([$have_visibility])
+	    if test x$have_visibility != xno; then
+		symbol_visibility=$VISIBILITY_CFLAGS
+		XORG_CFLAGS="$XORG_CFLAGS $VISIBILITY_CFLAGS"
+	    fi
+	fi
+	dnl added to xorg-server.pc
+	AC_SUBST([symbol_visibility])
+	dnl ===================================================================
+
 	PKG_CHECK_MODULES([PCIACCESS], [pciaccess >= 0.8.0])
 	SAVE_LIBS=$LIBS
 	SAVE_CFLAGS=$CFLAGS

xorg-server.pc.in

@@ -15,5 +15,5 @@ Name: xorg-server
 Description: Modular X.Org X Server
 Version: @PACKAGE_VERSION@
 Requires: pixman-1 pciaccess
-Cflags: -I${sdkdir}
+Cflags: -I${sdkdir} @symbol_visibility@
 Libs: -L${libdir}