Implemented native gzip compression/decompression using zlib routines.

Compression levels of the output can be controlled with the "gds
compress [<value>]" command, where <value> 0 (default) is uncompressed
output, 6 is "normal" gzip compression, and 9 is maximum compression.

scripts/configure

@@ -5035,6 +5035,49 @@ $as_echo "#define HAVE___VA_COPY 1" >>confdefs.h
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for gzopen in -lz" >&5
+$as_echo_n "checking for gzopen in -lz... " >&6; }
+if ${ac_cv_lib_z_gzopen+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lz  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char gzopen ();
+int
+main ()
+{
+return gzopen ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_z_gzopen=yes
+else
+  ac_cv_lib_z_gzopen=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_z_gzopen" >&5
+$as_echo "$ac_cv_lib_z_gzopen" >&6; }
+if test "x$ac_cv_lib_z_gzopen" = xyes; then :
+
+$as_echo "#define HAVE_ZLIB 1" >>confdefs.h
+
+fi
+
+