bootstrap: Require GNU patch

The bootstrap.conf uses patch, let's require it.

Better than multiple messages:
  ./bootstrap.conf: line 84: patch: command not found

Mention it also in the INSTALL file.

Signed-off-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

INSTALL

@@ -20,6 +20,7 @@ configuring the GRUB.
 * GNU binutils 2.9.1.0.23 or later
 * Flex 2.5.35 or later
 * pkg-config
+* GNU patch
 * Other standard GNU/Unix tools
 * a libc with large file support (e.g. glibc 2.1 or later)
 

bootstrap.conf

@@ -70,6 +70,7 @@ autoconf   2.63
 automake   1.11
 gettext    0.18.3
 git        1.5.5
+patch      -
 tar        -
 "