Pretty-printer tests fail on rawhide

[Florian Weimer]

The new pretty-printer tests fail on rawhide.

The test framework has various problems (output not captured in .out 
files, GDB startup scripts not disabled).

The cause of the test failure seems to be that the pretty printers are 
not registered at all:

(gdb) gdb-test% info pretty-printer
global pretty-printers:
   builtin
     mpx_bound128

I'll get to this eventually, but if anyone has an idea how to fix this, 
I welcome suggestions.

Thanks,
Florian