misc guile-related fixes (branch yem/fixes)

Hello All!

Here are two patches intended to fix guile builds:
- in bdwgc, detect availability of getcontext
- add proper kconfig dependency to guile

A third patch to guile I kept in limbo until we have a way to reproduce the autobuild failures it is supposed to fix (I was not able to reproduce any of them).

Thanks to Samuel for the initial series. :-)

Regards,
Yann E. MORIN.

The following changes since commit 49b147ccbb807238009fde815ad68e953077bc3a:

linux: fix breakage from d4b2b032a00c9922c9efa144b014dc086a7e48f1 (2014-12-24 15:00:48 +0100)

are available in the git repository at:

git://git.busybox.net/~ymorin/git/buildroot yem/fixes

for you to fetch changes up to efeb5ff2d78fb77cfd65a2e4e3bbb78ec9bef3f0:

bdwgc: add patch automatically detecting for NO_GETCONTEXT need (2014-12-24 20:04:24 +0100)

----------------------------------------------------------------
Samuel Martin (1):
bdwgc: add patch automatically detecting for NO_GETCONTEXT need

Yann E. MORIN (1):
package/guile: needs libtool

 ...ac-add-check-for-NO_GETCONTEXT-definition.patch | 28 ++++++++++++++++++++++
 package/guile/Config.in                            |  1 +
 2 files changed, 29 insertions(+)
 create mode 100644 package/bdwgc/0001-configure.ac-add-check-for-NO_GETCONTEXT-definition.patch

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