5855 fix __RESTRICT_KYWD to support the correct keyword with c++
<added 19/04/2015>

I believe the description should reflect now the fact that these are rectifications

to what gnu C does in fix-includes for c++ purposes. This permits the same with

non g++/clang++ compilers such as sunstudio CC.
Perhaps:

    5855 update posix_spawn[p] with rectified __RESTRICT_KYWD enabling 'restrict' semantics for both C and C++

The gate (on illumos-omnios) builds clean, lint-clean and shadow-compiler clean.
I've tested with both Sun C++ 5.9 SunOS_i386 Patch 124864-12 2009/04/21

and Sun C++ 5.10 SunOS_i386 128229-02 2009/09/21
I've also bootstrapped gcc (primarily 4.9.x now without my patch) and it swallows the good version just fine

as expected.
[update 2/07/2015]

I was mistaken, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61649 still needs to commit otherwise the

    #ifdef __cplusplus

    ...

clause is doubled causing warnings, so I've asked again for a commit of the patches provided to gcc.