Y2038: Include proper header to provide support for struct timeval on HURD

The HURD requires explicit inclusion of <bits/types/struct_timeval.h> to use
struct timeval in ./include/time.h.
For this particular glibc port, the proper header hasn't been included before
inclusion of time.h.

Tested with build-many-glibcs.py with i686-gnu and x86_64-linux-gnu:

build-many-glibcs.py /home/lukma/work/glibc/glibc-many-build --keep all compilers i686-gnu
build-many-glibcs.py /home/lukma/work/glibc/glibc-many-build --keep all glibcs i686-gnu

Also run of xcheck on x86_64:
./src/configure --prefix=/usr
make PARALLELMFLAGS="-j12" && make xcheck PARALLELMFLAGS="-j12"

	* include/time.h: Add #include <bits/types/struct_timeval.h>