automatically test ini file extension for files from commandline option @filename

automatically test ini file extension for files from commandline option @filename

The winboard.c is a patch that automatically tries indirection files on the
command line (@filename type arguments) also with an extension .ini if the name itself
did not match any existing file and contained no period. This saves the user typing the
.ini all the time (which I started to find pretty annoying while working on the installer
package).