dnl This is not a general checking macro, just a shorthand for repeated code as we look for several ZIP libraries.
dnl It uses our variables like enable_zip and found_zip.
AC_DEFUN([GWY_ZIP],
[
AC_REQUIRE([PKG_CHECK_MODULES])dnl
if test "x$found_zip" = xno && test "x$enable_zip" = x$1 -o "x$enable_zip" = xauto; then
    PKG_CHECK_MODULES(m4_toupper($1), [$2],
                      [AC_DEFINE(HAVE_[]m4_toupper($1),1,[Define if we have the ifelse($3,,$1,$3) package.])
                      found_zip=yes
                      zip_library=$1
                      ZIP_CFLAGS=$m4_toupper($1)_CFLAGS
                      ZIP_LIBS=$m4_toupper($1)_LIBS
                      ],[:])
fi
])
