#13 execute waits for the wrong child + possible memory leak in execute

[Xyandir]

Hi,
in the current version of pidgin (2.10.7) under linux there is a bug which creates zombie-processes.
Unfortunatly the current implementation of the execute command in pidgin-latex only uses wait, therefore it returns immediately.
My solution to fix this, is replacing line 261
"if( wait(&exitstatus)>0)"
with
"if( waitpid(child_id,&exitstatus,0)>0)"
which will wait for the child which was spawned by execute.
And while I was searching through this, I think the line 263 "free(opt);" has to be moved in front of the if, otherwise opt wouldn't be freed when wait has an error.
(sorry that I can't create a diff with the changes, but one piece of software which I don't understand is enough for one day)