Detect the X11 library on Solaris x86

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401374

configure.in

@@ -762,6 +762,7 @@ AC_HELP_STRING([--enable-x11-shared], [dynamically load X11 support [default=yes
                     x11ext_lib='libXext.so'
                     ;;
                 *)
+                    if test x$X_LIBS = x; then X_LIBS="-L/usr/lib"; fi
                     x11_lib_spec=`echo $X_LIBS | sed 's/.*-L\([[^ ]]*\).*/\1\/libX11.so.*/'`
                     x11_lib=`ls $x11_lib_spec | sed 's/.*\/\(.*\)/\1/; q'`
                     x11ext_lib_spec=`echo $X_LIBS | sed 's/.*-L\([[^ ]]*\).*/\1\/libXext.so.*/'`