git: Fix up <utmp.h> and <utmpx.h> for C++ programs.

[Sascha Wildner]

On 1/30/2011 22:52, Sascha Wildner wrote:
[...]
     so the functions can be called from C++ code (see the definition of
     __BEGIN_DECLS in<sys/ctype.h>).
[...]
Oops, I meant <sys/cdefs.h> there.

S.