A memory allocation failure happening in mworker_env_to_proc_list when
trying to allocate a mworker_proc would have resulted in a crash. This
function is only called during init.
It was raised in GitHub issue #1233.
It could be backported to all stable branches.
Only mworker uses proc_self, and it was declared in global.h, forcing
users of global.h to include mworker and its dependencies.
Moving it to mworker reduces the preprocessed size of version.c from
170 to 125kB by shrinking the number of local includes from 30 to 16
and the number of system includes from 147 to 132.
One function prototype makes reference to struct mworker_proc which was
not defined there but in global.h instead. This definition, along with
the PROC_O_* fields were moved to mworker-t.h instead.
