Add the basic structures for the netinet/in.h header.

Add some of the basic structures and stub functions for sys/socket.h

Implement strstr() and strpbrk() from string.h

Update cbindgen and fix issues with signal

The sigaction struct should not be a typedef, but the sigset_t struct
should be a typedef.

Update cbindgen to parse modules with a path attribute and revert the
following commits:
 - 996fad70.
 - cfe98ab3.

Actual working tests on strspn and strcspn

Yet another fix for strcspn and strspn.

Add the no_mangle attribute to fns

Add the no_mangle attribute to functions without it.

Change the type of byteset from [u8] to [usize] in strcspn and strspn. Hopefully this is the last bug in these!

Add missing extern crate statements

Add missing extern crate statements.

stat is now autogenerated correctly

The rusage struct makes use of the timeval structure. Make sure to
include sys/time.h so that the type is known.

Add SIZE_MAX to stdint.h

sys/resource expects the defined structures to not be defined with a
typedef.