Fix build for external boost 1.56.0

exception/detail/attribute_noreturn.hpp has been removed in 1.56. We
shouldn't have used a detail header in the first place. In master
we can use GMX_ATTRIBUTE_NORETURN but 5.0.x it is defined only
for code analysis not for compilers.

Change-Id: I6f26d6ddc62c73f583d324f7c794a499c274b394