games/simutrans: Fix build with Clang 6

gui/simwin.cc:503:11: error: case value evaluates to -1, which cannot be narrowed to type 'uint32' (aka 'unsigned int') [-Wc++11-narrowing]

case magic_none: return;
     ^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475044_s336572/logs/simutrans-120.2.2.log

• While here apply dos2unix and fix patch line endings