We don't currently use fork anywhere (or if we do it's by mistake!), so

We don't currently use fork anywhere (or if we do it's by mistake!), so
this patch strips down syscall.[Ch] so it now contains only the system
call interface. This interface is very, very simple! At the same time
I've taken the opportunity to remove syscontr.[Ch] and syssingleton.C,
again because they aren't used.

The rest of the changes are due to the change of name in the
Systemcall::Starttype enum. System is now Wait, and SystemDontWait is DontWait

Paves the way for resurrecting a proper forked calls controller.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@3553 a592a061-630c-0410-9148-cb99ea01b6c8