[BRLTTY] Baum driver test and backtrace from display powerdown

[Jason White]

After the fix to the Baum driver, BRLTTY runs under electric fence without
triggering a crash under normal operation (with the -N option to disable
BRLAPI).

However, after allowing the display to power down due to the idle timer, the
electric fence was triggered, resulting in a core file with the following
backtrace.

Core was generated by `/bin/brltty -N'.
Program terminated with signal 4, Illegal instruction.
#0  0x00002b2ddd6400c7 in kill () from /lib/libc.so.6
(gdb) bt
#0  0x00002b2ddd6400c7 in kill () from /lib/libc.so.6
#1  0x00002b2ddcffd053 in EF_Abort () from /usr/lib/libefence.so.0.0
#2  0x00002b2ddcffcc04 in memalign () from /usr/lib/libefence.so.0.0
#3  0x00002b2ddcffcc97 in malloc () from /usr/lib/libefence.so.0.0
#4  0x00002b2ddcffcd4a in realloc () from /usr/lib/libefence.so.0.0
#5  0x00002b2dde0a3ccc in reallocateTable (reference=0x2b2dddfd4f28, size=2, 
    count=0) at ./config.y:62
#6  0x00002b2dde0a3ebe in finishCurrentTerminal () at ./config.y:108
#7  0x00002b2dde0a3f3b in addTerminal (identifier=1) at ./config.y:117
#8  0x00002b2dde0a5004 in yyparse () at ./config.y:380
#9  0x00002b2dde0a5b33 in parseConfigurationFile () at ./config.y:647
#10 0x00002b2dde0a5bc1 in loadConfigurationFile (
    path=0x2b2dddfbffe4 "/etc/brltty/brltty-pm.conf") at ./braille.c:73
#11 0x00002b2dde0a8ad0 in brl_open (brl=0x64da60, parameters=0x2b2dddfa3fd8, 
    device=0x2b2ddda26ff8 "usb:") at ./braille.c:1383
#12 0x0000000000413e6e in openBrailleDriver () at ./config.c:1386
#13 0x0000000000414223 in activateBrailleDriver (verify=0) at ./config.c:1491
#14 0x00000000004146d4 in startBrailleDriver () at ./config.c:1605
#15 0x0000000000414753 in restartBrailleDriver () at ./config.c:1630
#16 0x000000000040de5e in main (argc=2, argv=0x7fffcdad6728) at ./main.c:1600