Rewrite grub-install, grub-mkrescue, grub-mkstandalone and grub-mknetdir

the function of these files exceeds what can be sanely handled in shell
	in posix-comaptible way. Also writing it in C extends the functionality
	to non-UNIX-like OS and minimal environments.

grub-core/osdep/unix/compress.c

@@ -0,0 +1,41 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2013 Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/emu/exec.h>
+#include <grub/util/install.h>
+
+int 
+grub_install_compress_gzip (const char *src, const char *dest)
+{
+  return grub_util_exec_redirect ((const char * []) { "gzip", "--best",
+	"--stdout", NULL }, src, dest);
+}
+
+int 
+grub_install_compress_xz (const char *src, const char *dest)
+{
+  return grub_util_exec_redirect ((const char * []) { "xz",
+	"--lzma2=dict=128KiB", "--check=none", "--stdout", NULL }, src, dest);
+}
+
+int 
+grub_install_compress_lzop (const char *src, const char *dest)
+{
+  return grub_util_exec_redirect ((const char * []) { "lzop", "-9",  "-c",
+	NULL }, src, dest);
+}