Replace `mkinstalldirs' with AC_PROG_MKDIR_P. * builds/unix/mkinstalldirs: Removed, no longer needed. * builds/unix/configure.raw: Call `AC_PROG_MKDIR_P'. Update pwd call for `$INSTALL'. * builds/unix/unix-def.in (MKINSTALLDIRS): Use `@MKDIR_P@'. * autogen.sh: Updated.