kconfig: prepend CT-NG's version tag to PKGVERSION

"crosstool-NG-${CT_VERSION}" is currently the default for TOOLCHAIN_PKGVERSION,
and this options is passed as is to --with-pkgversion.

This patch prepends "crosstool-NG ${CT_VERSION}" to TOOLCHAIN_PKGVERSION before
passing it to --with-pkgversion.

Signed-off-by: "Benoît THÉBAUDEAU" <benoit.thebaudeau@advansee.com>

functions: save & restore the static companion libraries install dir

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

functions: fix downloading files

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

cc/gcc: CC_STATIC_LIBSTDCXX 'depends on' CONFIGURE_has_static_libstdcpp

Hide the staticaly linked libstdc++ option if the static libstdc++ is not
present, detected at configure time.

Add a blind option that says whether static linking is possible at all.
It defaults to 'y', but depends on the needed CONFIGURE_* options. For
now, it only depends on static libtdc++, but new dependencies can be
easily added.

Hide the global static toolchain option behind this new option.

Original patch by Bryan Hundven <bryanhundven@gmail.com>

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

configure: check for libstdc++.{so,dylib,a}

It's probably a good thing to check for at least one instance of
libstdc++.{so,dylib,a} at configure time. At least one is needed
by the companion libraries and gcc.

Original patch by Bryan Hundven <bryanhundven@gmail.com>

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

configure: add prefix to err messages in has_or_{abort,warn}

Make it easier to spot messages spewed out by has_or_{abort,warn}.

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

configure: maintain single quotes in error messages

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