VcsCommand: Add std channel getters

Conform to QtcProcess interface and provide cleanedStdOut()
and cleanedStdErr() getters, to be called after the process
finished.

Use cleanedStdOut() inside DiffEditorController for getting
the output after the process finished instead of connecting
to stdOutText() signal.

Change-Id: I7ba3735b0ab2167ac1f3b0954dd5dc9553910aac
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/vcsbase/vcscommand.cpp

@@ -372,6 +372,16 @@ void VcsCommand::cancel()
     emit terminate();
 }
 
+QString VcsCommand::cleanedStdOut() const
+{
+    return d->m_stdOut;
+}
+
+QString VcsCommand::cleanedStdErr() const
+{
+    return d->m_stdErr;
+}
+
 CommandResult VcsCommand::runCommand(const CommandLine &command, int timeoutS)
 {
     QtcProcess process;