Append a new string entry to the property list, possibly
* overwriting an already existing entry with the same key. An
* internal copy of the data passed is made. Will accept only valid
* UTF-8. The data can be passed as printf()-style format string with
* arguments. Returns zero on success. \since 0.9.11
Append a new string entry to the property list, possibly * overwriting an already existing entry with the same key. An * internal copy of the data passed is made. Will accept only valid * UTF-8. The data can be passed as printf()-style format string with * arguments. Returns zero on success. \since 0.9.11