Issues #88: sometimes the end of the heap of the DF process will change
between detaching and re-attaching to the process. To deal with this,
/proc/PID/maps is re-read every time the process is attached.
Also, made semgent finder give a little more info if there's an error
doing a memory read.
The dfincremental ui does not allow entering strings with trailing
whitespace, and anyway sometimes it is difficult to guess how a GUI
string actually ends. Therefore it is probably more generic to
search for buffers that simply begin with the entered string.
Matthew Cline
Alexander Gavrilov
Petr Mrázek
Tom Prince