Add optional Win32 console allocation

This patch adds the optional --win32console command line option.
It does nothing on OSx and Linux, while is only useable on Win32.

On Win32 if the application was built as GUI (not console),
there is no way to view stdout and stderr. With windows.c's
subsurface_console_init() we are able to either redirect
stdout and stderr to the terminal from which subsurface.exe
was started (always happens; --win32console does nothing in
this case) or if --win32console is explicitly added to
a shortcut, create a dedicated console window and monitor
the output there.

if set, WIN32_CONSOLE_APP is a condition that will make the
subsurface_console_init() and subsurface_console_exit()
functions NOP on Windows. The definition will be created if
the user passes 'CONFIG += console' to qmake.

Fixes #436

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

linux.c

@@ -131,3 +131,14 @@ int subsurface_zip_close(struct zip *zip)
 {
 	return zip_close(zip);
 }
+
+/* win32 console */
+void subsurface_console_init(bool dedicated)
+{
+	/* NOP */
+}
+
+void subsurface_console_exit(void)
+{
+	/* NOP */
+}