[Bug 38337] clang compiling warnings

https://bugs.winehq.org/show_bug.cgi?id=38337

--- Comment #21 from Sergey Isakov  ---
/Volumes/MacHD/Users/sergey/Documents/Projects/winehq/dlls/winex11.drv/pen.c:50:56:
warning: implicit conversion from 'int' to 'char' changes value from 255 to -1
[-Wconstant-conversion]
    for (i = 0; i < pos; i++) res[i] = min( dashes[i], 255 );
                                     ~                 ^~~
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signed <-> unsigned errors again