brltty: new package

Signed-off-by: Mario Lang <mlang@blind.guru>
[Thomas:
 - wrap too long CONF_OPTS line that disables all the language
   bindings
 - use an intermediate BRLTTY_TEXT_TABLE variable to store the
   qstripped version of BR2_PACKAGE_BRLTTY_TEXT_TABLE.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>