[LyX/2.2-staging] Add a comment for the special code on Windows

[Vincent van Ravesteijn]

commit 3c67d6f77c54eaff70e1f6ce6c80b81e26c9b56d
Author: Vincent van Ravesteijn <v...@lyx.org>
Date:   Wed Mar 19 21:07:43 2014 +0100

    Add a comment for the special code on Windows

diff --git a/src/support/Systemcall.cpp b/src/support/Systemcall.cpp
index c42ed0c..de5de61 100644
--- a/src/support/Systemcall.cpp
+++ b/src/support/Systemcall.cpp
@@ -251,6 +251,11 @@ int Systemcall::startscript(Starttype how, string const & 
what,
        SystemcallPrivate d(infile, outfile, errfile);
 
 #ifdef Q_OS_WIN32
+       // QProcess::startDetached cannot provide environment variables. When 
the
+       // environment variables are set using the latexEnvCmdPrefix and the 
process
+       // is started with QProcess::startDetached, a console window is shown 
every 
+       // time a viewer is started. To avoid this, we fall back on Windows to 
the 
+       // original implementation that creates a QProcess object.
        d.startProcess(cmd, path, false);
        if (!d.waitWhile(SystemcallPrivate::Starting, process_events, -1)) {
                LYXERR0("Systemcall: '" << cmd << "' did not start!");