[PATCH] ash: fix SEGV in parsebackq on big buffers caused by alloca

[Ron Yorston]

Martin,

Try my patch 'ash: preserve characters on heap in backquote parsing'
from Nov 11 instead.

The trouble with using malloc/free is that it can leak memory if an
exception is raised.

We used to use malloc/free.  See commit 072fc60f2 'ash: use alloca to
get rid of setjmp' for an idea of the amount of code that's needed to
handle exceptions correctly.

Ron