CppTools: Fix completion in other editor

On duplication of an editor onMimeTypeChanged() of CppToolsEditorSupport
was not triggered, thus not completion provider was set.

Task-number: QTCREATORBUG-10284

Change-Id: Ia1da7f59b19e042f65b068a993f0d5c04b0778e0
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
ProParser: Plug raw data leak

QProcessEnvironment caches keys, so we must not pass it QStrings created with
fromRawData()

Task-number: QTCREATORBUG-9142
Change-Id: I29fade02f3bc4110fafb1b04d44f2e653951a2ae
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>