Re-enable grub-extras.

* autogen.sh: Create symlinks to ${GRUB_CONTRIB} if necessary to
avoid confusing Automake.  Run autogen only twice, once for the top
level and once for grub-core.  Add Makefile.util.def and
Makefile.core.def from extra modules to the appropriate autogen
invocations.  If Makefile.common exists in an extra module, include
it in both Makefile.util.am and grub-core/Makefile.core.am;
similarly, include any Makefile.util.common file in Makefile.util.am
and any Makefile.core.common file in grub-core/Makefile.core.am.
* conf/Makefile.common ($(top_srcdir)/grub-core/Makefile.core.am):
Depend on $(top_srcdir)/grub-core/Makefile.gcry.def.
($(top_srcdir)/grub-core/Makefile.gcry.def): Remove.
* grub-core/Makefile.am: Remove inclusion of Makefile.gcry.am.
* gentpl.py (gvar_add): Turn GVARS into a set.
(global_variable_initializers): Sort global variables on output.
(vars_init): New function.
(first_time): Likewise.
(library): Ensure that non-global variable initialisations are
emitted before the first time we emit code for a library block.
Append to variables rather than setting them.  Only emit
noinst_LIBRARIES, BUILT_SOURCES, and CLEANFILES the first time for
each conditional path.
(program): installdir() emits an Autogen macro, so must be passed to
var_add rather than gvar_add.
(data): Likewise.
(script): Likewise.
(rules): New function, centralising handling for different target
types.  Set up Guile association lists for first_time and vars_init,
and send most output to a diversion so that variable initialisations
can be emitted first.
(module_rules): Use new rules function.
(kernel_rules): Likewise.
(image_rules): Likewise.
(library_rules): Likewise.
(program_rules): Likewise.
(script_rules): Likewise.
(data_rules): Likewise.
* configure.ac: Add AC_PROG_LN_S, for the benefit of ntldr-img.
* .bzrignore: Add contrib and grub-core/contrib.  Remove
grub-core/Makefile.gcry.am.

configure.ac

@@ -235,6 +235,7 @@ AC_PROG_LEX
 AC_PROG_YACC
 AC_PROG_MAKE_SET
 AC_PROG_MKDIR_P
+AC_PROG_LN_S
 
 if test "x$LEX" = "x:"; then
   AC_MSG_ERROR([flex is not found])