* gdb.base/sigbpt.exp: Detect which signal is received when a NULL
pointer is dereferenced and use this signal name in regexp.
* gdb.base/signull.exp: Ditto.
* gdb.base/sigbpt.c (main): Catch SIGBUS too.
* gdb.base/signull.c (main): Ditto.
* gdb.base/signull.c: Update copyright. Include <string.h>.
(bowler): Replace data_pointer with data_read
and data_write cases. Add code_descriptor case.
(zero, desc): New array and pointer.
(data, code): Change to simple pointers.
* gdb.base/signull.exp: Fix probe pattern matching a function
descriptor SIGSEGV. Replace data_pointer with data_read and
data_write tests.