message: Add PURGE_* constants for use with PurgeComm function
diff: @@ -321,7 +321,10 @@ pub const CLRDTR: DWORD = 6;
  pub const RESETDEV: DWORD = 7;
  pub const SETBREAK: DWORD = 8;
  pub const CLRBREAK: DWORD = 9;
  -// PURGE_*
  +pub const PURGE_TXABORT: DWORD = 0x0001;
  +pub const PURGE_RXABORT: DWORD = 0x0002;
  +pub const PURGE_TXCLEAR: DWORD = 0x0004;
  +pub const PURGE_RXCLEAR: DWORD = 0x0008;
  pub const MS_CTS_ON: DWORD = 0x0010;
  pub const MS_DSR_ON: DWORD = 0x0020;
  pub const MS_RING_ON: DWORD = 0x0040;
  