* zlib.m4: New file.

config/zlib.m4

@@ -0,0 +1,18 @@
+dnl A function to check for zlib availability.  zlib is used by default
+dnl unless the user configured with --disable-nls.
+
+AC_DEFUN([AM_ZLIB],
+[
+  # See if the user specified whether he wants zlib support or not.
+  AC_ARG_WITH(zlib,
+    [  --with-zlib             include zlib support (auto/yes/no) [default=auto]],
+    [], [with_zlib=auto])
+
+  if test "$with_zlib" != "no"; then
+    AC_SEARCH_LIBS(zlibVersion, z, [AC_CHECK_HEADERS(zlib.h)])
+    if test "$with_zlib" = "yes" -a "$ac_cv_header_zlib_h" != "yes"; then
+      AC_MSG_ERROR([zlib (libz) library was explicitly requested but not found])
+    fi
+  fi
+])
+