The gatresult data types embeds GSList members, and the function
prototypes uses glib types.
Add include of glib.h to allow use of gatresult.h without also including
glib.h
Currently next_string and next_hexstring functions use a static
buffer in the iterator to store the value. This value is clobbered
as soon as next_string or next_hexstring is called. Instead,
we copy the entire line in iter_next and use it as a scratch buffer.
The only limitation is that lines of max 2048 are possible, however
these are limited to around this size by parts of the standard.