gen: clarify usage of 'self' as parent PID
gen: clarify usage of 'self' as parent PID

The atom `self` is used instead of parent PID for processes without a
parent, like in the case of monitor or link. The use of the atom `self`
could be mistaken for a typo.

This patch changes the atom declaration to use single quotes to clarify
the intended use of `'self'` as an atom and hopefully removes the
possibility that `'self'` is interpreted as a typo when read by a fellow
developer.

erlang/otp,bjorng/otp,bjorng/otp,uabboli/otp,mikpe/otp,uabboli/otp,bjorng/otp,dumbbell/otp,jj1bdx/otp,mikpe/otp,vinoski/otp,potatosalad/otp,emacsmirror/erlang,g-andrade/otp,rlipscombe/otp,isvilen/otp,vinoski/otp,jj1bdx/otp,uabboli/otp,potatosalad/otp,jj1bdx/otp,rlipscombe/otp,emacsmirror/erlang,vinoski/otp,getong/otp,vinoski/otp,emacsmirror/erlang,mikpe/otp,mikpe/otp,dgud/otp,vinoski/otp,g-andrade/otp,dumbbell/otp,isvilen/otp,potatosalad/otp,jj1bdx/otp,potatosalad/otp,emacsmirror/erlang,ferd/otp,isvilen/otp,potatosalad/otp,mikpe/otp,jj1bdx/otp,vinoski/otp,getong/otp,uabboli/otp,dgud/otp,uabboli/otp,dgud/otp,g-andrade/otp,g-andrade/otp,rlipscombe/otp,bjorng/otp,uabboli/otp,rlipscombe/otp,jj1bdx/otp,potatosalad/otp,g-andrade/otp,vinoski/otp,getong/otp,ferd/otp,isvilen/otp,jj1bdx/otp,mikpe/otp,getong/otp,erlang/otp,bjorng/otp,getong/otp,getong/otp,uabboli/otp,potatosalad/otp,dumbbell/otp,isvilen/otp,dumbbell/otp,erlang/otp,g-andrade/otp,mikpe/otp,dumbbell/otp,dgud/otp,bjorng/otp,emacsmirror/erlang,dgud/otp,ferd/otp,dumbbell/otp,ferd/otp,uabboli/otp,jj1bdx/otp,rlipscombe/otp,ferd/otp,isvilen/otp,dgud/otp,erlang/otp,isvilen/otp,g-andrade/otp,bjorng/otp,dgud/otp,getong/otp,dumbbell/otp,dgud/otp,vinoski/otp,ferd/otp,emacsmirror/erlang,potatosalad/otp,g-andrade/otp,erlang/otp,mikpe/otp,bjorng/otp,emacsmirror/erlang,isvilen/otp,getong/otp,getong/otp,vinoski/otp,mikpe/otp,rlipscombe/otp,ferd/otp,jj1bdx/otp,jj1bdx/otp,emacsmirror/erlang,bjorng/otp,vinoski/otp,getong/otp,isvilen/otp,ferd/otp,dgud/otp,rlipscombe/otp,g-andrade/otp,uabboli/otp,erlang/otp,rlipscombe/otp,dumbbell/otp,rlipscombe/otp,ferd/otp,dumbbell/otp,rlipscombe/otp,erlang/otp,bjorng/otp,erlang/otp,potatosalad/otp,mikpe/otp,emacsmirror/erlang,dumbbell/otp,emacsmirror/erlang,dgud/otp,potatosalad/otp,erlang/otp,isvilen/otp,g-andrade/otp,erlang/otp