configure: add possibility to set arbitrary variable in check_for

If check_for is able to find the required prog/inc/lib, allow it to
set an arbitrary variable to 'y'. This variable is then pushed down
to the kconfig definition.

For example:
has_or_abort prog=foobar kconfig=has_foobar

If foobar is available, it yields a kconfig variable defaulting to y:
config CONFIGURE_has_foobar
bool
default y

If foobar is missing, it yields a kconfig variable defaulting to n:
config CONFIGURE_has_foobar
bool

Thus it is possible to depends on that variabel to show/hide options:
config SOME_FEATURE
bool
prompt "Some feature"
depends on CONFIGURE_has_foobar

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

2008-06-07  Mike Frysinger  <vapier@gentoo.org>

	* sysdeps/unix/sysv/linux/alpha/sys/user.h: Copy page.h definitions

	from the kernel header to sys/user.h and remove the #include of

	sys/user.h.

--- a/sysdeps/unix/sysv/linux/alpha/sys/user.h

+++ b/sysdeps/unix/sysv/linux/alpha/sys/user.h

@@ -23,7 +23,6 @@

    only. Don't read too much into it. Don't use it for anything other

    than gdb/strace unless you know what you are doing. */

-#include <asm/page.h>

 #include <asm/reg.h>

 struct user

@@ -41,6 +40,9 @@ struct user

   char u_comm[32];				/* user command name */

 };

+#define PAGE_SHIFT		13

+#define PAGE_SIZE		(1 << PAGE_SHIFT)

+#define PAGE_MASK		(~(PAGE_SIZE-1))

 #define NBPG			PAGE_SIZE

 #define UPAGES			1

 #define HOST_TEXT_START_ADDR	(u.start_code)