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>

--- trunk/src/acos.c	2009/12/08 16:49:43	733

+++ trunk/src/acos.c	2009/12/09 20:51:38	734

@@ -188,10 +188,7 @@

   else

     rnd_im = rnd_im == GMP_RNDU ? GMP_RNDD

       : rnd_im == GMP_RNDD ? GMP_RNDU

-#if MPFR_VERSION_MAJOR >= 3

-      : rnd_im == GMP_RNDA ? GMP_RNDZ

-#endif

-      : rnd_im;

+      : rnd_im; /* both RNDZ and RNDA map to themselves for -asin(z) */

   rnd1 = RNDC(GMP_RNDN, rnd_im);

   mpfr_init2 (pi_over_2, p);

   for (;;)