fix: never leave Steam a file it would reinstall itself over

The patch that keeps the script's length was the good path and appending was
the fallback, with -noverifyfiles on everything that starts Steam to cover for
it. That cover does not exist.

Steam checks its files at the shutdown it runs itself, not only at a start
somebody handed arguments to, and that run carries no -noverifyfiles whatever
the session was started with. One wrong length there costs the whole client
package downloaded, extracted and installed again - and the client quits at the
end of it instead of coming up, which is the "Steam just closed itself" that
this was seen as:

    BVerifyInstalledFiles: steamwebhelper.sh is 130 bytes, expected 84
    Update wird heruntergeladen ... Paket wird extrahiert ...
    Aktualisierung abgeschlossen, Steam wird geladen ... Shutdown

So the flag now either fits in the space the comments give back or it is not
written at all, and the status screen says Steam is not patched. No autoscroll
in the interface is a far smaller thing than a client that reinstalls itself.

With no growing patch left to prop up, -noverifyfiles has nothing to do and is
gone with everything that carried it: Steam's launcher entry, its autostart
entry, the shortcuts on the desktop and the ones it writes for single games.
Steam repairs its own installation again. An installation from an older version
is taken back once through the flag scheme, and a patch that version appended
is rebuilt to fit at the next apply - or taken back, if the comments cannot pay
for it.

src/lib/common.sh

@@ -45,10 +45,14 @@ MCA_BROWSER_FLAG="--enable-features=MiddleClickAutoscroll,HeliumMiddleClickAutos
 MCA_FEATURE="MiddleClickAutoscroll"
 MCA_BROWSER_FEATURES="MiddleClickAutoscroll,HeliumMiddleClickAutoscroll"
 
-# Bumped when the flags above change. An installation that was set up by a
-# version with a different answer is taken back and done again once, because a
-# file that is already patched is otherwise left alone. See mca_apply.
-MCA_FLAG_SCHEME=2
+# Bumped when the flags above change, and when what gets written where does.
+# An installation that was set up by a version with a different answer is taken
+# back and done again once, because a file that is already patched is otherwise
+# left alone. See mca_apply.
+#
+# 3 is what takes -noverifyfiles back out of the Steam entries an older version
+# put it in.
+MCA_FLAG_SCHEME=3
 
 MCA_LIBDIR="${MCA_LIBDIR:-@LIBDIR@}"
 MCA_LOCALEDIR="${MCA_LOCALEDIR:-@LOCALEDIR@}"