base/filepush.cpp: Stop background thread in eFilePushThread destructor

The eThread class has a design fault: Classes are supposed to inherit
from it. This can't work in C++, because once the eThread d'tor fires,
the object has alread been demoted and partially destroyed. This
results in the thread now running with halfway destroyed data.

A workaround is to always join the thread in each class that inherits
from eThread, which is what this commit implements.

A proper fix would be to remove all virtual methods from eThread, and
use a "runnable" or similarly named member to actually implement the
thread's code.
eFixedMessagePump: Remove unused start/stop methods

No one ever calls start or stop on it, so remove these.
Since it calls "start()" manually, pass "false" for the "startnow"
parameter of the eSocketNotifier constructor.
Merge branch 'master' of git://git.code.sf.net/p/openpli/enigma2