Add libintl link flags to SVN_INTL_LIBS on *nix builds. The SVN_INTL_LIBS variable was referred to but never defined. * Makefile.in: Define SVN_INTL_LIBS. * configure.ac: Set SVN_INTL_LIBS to the linker flags required to link to libintl and export the value of SVN_INTL_LIBS to the Makefile.