changed obsolete automake macro

po/Makefile.in.in

@@ -33,7 +33,7 @@ gettextsrcdir = $(datadir)/gettext/po
 INSTALL = @INSTALL@
 INSTALL_DATA = @INSTALL_DATA@
 mkinstalldirs = $(SHELL) @install_sh@ -d
-mkdir_p = @mkdir_p@
+mkdir_p = @MKDIR_P@
 
 GMSGFMT_ = @GMSGFMT@
 GMSGFMT_no = @GMSGFMT@