Reads a line, including the terminating character(s), from a IOChannel into a newly-allocated string.
str_return will contain allocated memory if the return is g_io_status_normal.
The line read from the IOChannel, including the line terminator. This data
should be freed with g_free when no longer needed. This is a nul-terminated
string. If a
location to store length of the read data, or null
location to store position of line terminator, or null
the status of the operation.