Compatibility with SILKey for the Apple Macintosh

Keyman supports some special codes at the start of the line to identify Keyman-only lines and ignore SILKey-only lines. These codes are:

$weaver:      c A SILKey-only line; Keyman will ignore 
              c the rest of the line

$keyman:      c Keyman will strip out the $keyman: text 
              c and process the rest of the line normally