MFC r316552,r319662:

r316552:

atf-c: fix documentation description for atf_utils_wait(3)

atf_utils_wait(3) should be used in combination with atf_utils_fork(3),
not itself (atf_utils_wait(3)).

r319662:

Add MLINKS for atf-sh(3) to each of the functions it implements

This hopefully will make atf-sh(3) easier to understand for newcomers,
without having to go through the atf-sh(3) level of indirection.