2006-09-19 Marcus Brinkmann <marcus@g10code.de>

• mkerrors (_assuan_error): Change return type to assuan_error_t.
• assuan-buffer.c (_assuan_read_line): Change return type to

assuan_error_t. Map returned value of -1.
(_assuan_write_line): Change type of RC to assuan_error_t.

• assuan-defs.h (_assuan_read_line, _assuan_error): Likewise for

prototypes.