Moved additional gmxlib sources to C++

Moved functions into std:: namespace and changed try->attempt
to avoid using reserved names. gmx_cpuid.c has been left
as C for now, both because __cpuid() and __cpuidex() does
not appear to be present in C++ source, and because it will
anyway be replaced with a proper C++ module that can also
interface to hwloc.

Change-Id: I6f10b19a499209b375ee154540a3386f882457bd