doc: Update for MSVC 14

Hi, I'm updating the doc regarding MSVC 14 a.k.a. Visual C++ 2015 [1] (as compared to MSVC 9). The patch is at http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=8fb59b8fac140205a6a0ef3286b5fd5a58f418e1 But more important than the files that have changed are the files that still mention

Re: VMS has struct sched_param in pthread.h

> 2017-06-19 Bruno Haible > John E. Malmberg(tiny change) > > sched: Fix compilation failure on OpenVMS. > * m4/sched_h.m4 (gl_SCHED_H): Require AC_CANONICAL_HOST. On OpenVMS, > test whether exists and defines struct sched_param. > * lib/sched.in.h: On O