core: fix delayed warning display in emacs 25.5
core: fix delayed warning display in emacs 25.5

Discard the warnings produced when packages are byte-compiled which fix the
popup of the *Compile-Log* window at the end of the installation.
If emacs has been launch with argument `--debug-init` we don't discard the
warnings.

tsonntag/dotemacs,tsonntag/dotemacs,tsonntag/dotemacs,tsonntag/dotemacs