kernel/linux: fix using custom location

Currently, extract and patch are skipped as thus:
- using a custom directory of pre-installed headers
- a correctly named directory already exists

Otherwise, extract and patch are done.

The current second condition is wrong, because it allows the following
sequence to happen:
- a non-custom kernel is used
- a previous build only partially extracted the non-custom sources
- that p[revious build broke during extraction (eg. incomplete tarball...)
- a subsequent build will find a properly named directory, and will
thus skip extract and patch, which is wrong

Fix that by following the conditions in this table:

Type | Extract | Patch
----------------------+---------+-------
Pre-installed headers | N | N
custom directory | N | N
custom tarball | Y | N
mainstream tarball | Y | Y

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: David Holsgrove <david.holsgrove@xilinx.com>

If we're using a cvs snapshot which updates the source files, and

perl isn't installed yet, then we can't regen the docs.  Not a big

deal, so just whine a little and continue on our merry way.

http://bugs.gentoo.org/60132

diff -durN glibc-2.12.1.orig/manual/Makefile glibc-2.12.1/manual/Makefile

--- glibc-2.12.1.orig/manual/Makefile	2006-01-08 07:43:47.000000000 +0100

+++ glibc-2.12.1/manual/Makefile	2009-11-13 00:49:54.000000000 +0100

@@ -104,9 +104,14 @@

 libm-err.texi: stamp-libm-err

 stamp-libm-err: libm-err-tab.pl $(wildcard $(foreach dir,$(sysdirs),\

 						     $(dir)/libm-test-ulps))

+ifneq ($(PERL),no)

 	pwd=`pwd`; \

 	$(PERL) $< $$pwd/.. > libm-err-tmp

 	$(move-if-change) libm-err-tmp libm-err.texi

+else

+	echo "Unable to rebuild math docs, no perl installed"

+	touch libm-err.texi

+endif

 	touch $@

 # Generate Texinfo files from the C source for the example programs.