Fix compilation with Intel CC: C code can't have templates

wtf/Assertions.h is compiled in C, C++, Objective C and Objective C++
modes. The C++ parts need to be inside #ifdef __cplusplus, so make sure
the templates are hidden by it.

But since Intel CC version 13 does not need the trick anymore, we can
exclude it from there.

Change-Id: Ifa1b168feec31826ecd025d07067852456d41ba1
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>
Fix compilation with Intel CC

Inline functions must be defined. This one is meant not to be
defined, so don't mark it inline

Change-Id: Ibdf81302f88d568042ff5fc6733f96c8716fa52d
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>