bundle main sources read-only, to avoid accidental editing of imported theories etc.;

--- a/Admin/Windows/Cygwin/isabelle/postinstall	Sun Nov 22 23:19:43 2015 +0100
+++ b/Admin/Windows/Cygwin/isabelle/postinstall	Mon Nov 23 16:57:01 2015 +0100
@@ -9,6 +9,6 @@
 
 find -type d -exec chmod 755 '{}' +
 find -type f \( -name '*.exe' -o -name '*.dll' \) -exec chmod 755 '{}' +
-find -type f -not -name '*.exe' -not -name '*.dll' -exec chmod 644 '{}' +
+find -type f -not -name '*.exe' -not -name '*.dll' -not -name '*.scala' -not -name '*.ML' -not -name '*.thy' -exec chmod 644 '{}' +
+find -type f \( -name '*.scala' -o -name '*.ML' -o -name '*.thy' \) -exec chmod 444 '{}' +
 xargs -0 < contrib/cygwin/isabelle/executables chmod 755
-

--- a/Admin/lib/Tools/makedist	Sun Nov 22 23:19:43 2015 +0100
+++ b/Admin/lib/Tools/makedist	Mon Nov 23 16:57:01 2015 +0100
@@ -207,8 +207,9 @@
 echo "$IDENT" >../ISABELLE_IDENT
 
 chown -R "$LOGNAME" "$DISTNAME"
+chmod -R g=o "$DISTNAME"
 chmod -R u+w "$DISTNAME"
-chmod -R g=o "$DISTNAME"
+find "$DISTNAME" -type f "(" -name '*.scala' -o -name '*.ML' -o -name '*.thy' ")" -print | xargs chmod -f u-w
 
 echo "$DISTBASE/$DISTNAME.tar.gz"
 tar -c -z -f "$DISTNAME.tar.gz" "$DISTNAME"