Default the X11 dynamically loading on if the OS loader loads libraries

with their private symbols hidden.  If that isn't the case, and someone
tries to enable it anyway, spit out a warning and don't let them do it.

configure.in

@@ -813,12 +813,18 @@ AC_HELP_STRING([--enable-video-x11], [use X11 video driver [[default=yes]]]),
         AC_PATH_X
         AC_PATH_XTRA
         if test x$have_x = xyes; then
+            # Only allow dynamically loaded X11 if the X11 function pointers
+            # will not end up in the global namespace, which causes problems
+            # with other libraries calling X11 functions.
+            x11_symbols_private=$have_gcc_fvisibility
+
             AC_ARG_ENABLE(x11-shared,
-AC_HELP_STRING([--enable-x11-shared], [dynamically load X11 support [[default=yes]]]),
-                          , enable_x11_shared=yes)
+AC_HELP_STRING([--enable-x11-shared], [dynamically load X11 support [[default=maybe]]]),
+                          , enable_x11_shared=maybe)
 
             case "$host" in
                 *-*-darwin*) # Latest Mac OS X actually ships with Xrandr/Xrender libs...
+                    x11_symbols_private=yes
                     x11_lib='/usr/X11R6/lib/libX11.6.dylib'
                     x11ext_lib='/usr/X11R6/lib/libXext.6.dylib'
                     xrender_lib='/usr/X11R6/lib/libXrender.1.dylib'
@@ -837,27 +843,27 @@ AC_HELP_STRING([--enable-x11-shared], [dynamically load X11 support [[default=ye
                     for path in $x11_lib_path /usr/lib /usr/X11/lib /usr/X11R6/lib; do
                         if test "x$x11_lib" = "x"; then
                             x11_lib=[`ls -- $path/libX11.so.[0-9] 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							if test "x$x11_lib" = "x"; then
-								x11_lib=[`ls -- $path/libX11.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							fi
+                            if test "x$x11_lib" = "x"; then
+                                x11_lib=[`ls -- $path/libX11.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
+                            fi
                         fi
                         if test "x$x11ext_lib" = "x"; then
                             x11ext_lib=[`ls -- $path/libXext.so.[0-9] 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							if test "x$x11ext_lib" = "x"; then
-								x11ext_lib=[`ls -- $path/libXext.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							fi
+                            if test "x$x11ext_lib" = "x"; then
+                                x11ext_lib=[`ls -- $path/libXext.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
+                            fi
                         fi
                         if test "x$xrender_lib" = "x"; then
                             xrender_lib=[`ls -- $path/libXrender.so.[0-9] 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							if test "x$xrender_lib" = "x"; then
-								xrender_lib=[`ls -- $path/libXrender.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							fi
+                            if test "x$xrender_lib" = "x"; then
+                                xrender_lib=[`ls -- $path/libXrender.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
+                            fi
                         fi
                         if test "x$xrandr_lib" = "x"; then
                             xrandr_lib=[`ls -- $path/libXrandr.so.[0-9] 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							if test "x$xrandr_lib" = "x"; then
-								xrandr_lib=[`ls -- $path/libXrandr.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
-							fi
+                            if test "x$xrandr_lib" = "x"; then
+                                xrandr_lib=[`ls -- $path/libXrandr.so.[0-9]* 2>/dev/null | sort -r | sed 's/.*\/\(.*\)/\1/; q'`]
+                            fi
                         fi
                     done
                     ;;
@@ -873,13 +879,16 @@ AC_HELP_STRING([--enable-x11-shared], [dynamically load X11 support [[default=ye
             AC_DEFINE(SDL_VIDEO_DRIVER_X11)
             SOURCES="$SOURCES $srcdir/src/video/x11/*.c"
             EXTRA_CFLAGS="$EXTRA_CFLAGS $X_CFLAGS"
+
+            if test x$enable_x11_shared = xmaybe; then
+                enable_x11_shared=$x11_symbols_private
+            fi
             if test x$have_loadso != xyes && \
                test x$enable_x11_shared = xyes; then
                 AC_MSG_WARN([You must have SDL_LoadObject() support for dynamic X11 loading])
                 enable_x11_shared=no
             fi
-
-            if test x$have_gcc_fvisibility != xyes && \
+            if test x$x11_symbols_private != xyes && \
                test x$enable_x11_shared = xyes; then
                 AC_MSG_WARN([You must have gcc4 (-fvisibility=hidden) for dynamic X11 loading])
                 enable_x11_shared=no