Returns the value associated with key under group_name as a
boolean.
If key cannot be found then false is returned and error is set
to G_KEY_FILE_ERROR_KEY_NOT_FOUND. Likewise, if the value
associated with key cannot be interpreted as a boolean then false
is returned and error is set to G_KEY_FILE_ERROR_INVALID_VALUE.
Returns the value associated with key under group_name as a boolean.
If key cannot be found then false is returned and error is set to G_KEY_FILE_ERROR_KEY_NOT_FOUND. Likewise, if the value associated with key cannot be interpreted as a boolean then false is returned and error is set to G_KEY_FILE_ERROR_INVALID_VALUE.