The original buffer is f->nsubf*sizeof *subf bytes (oldsize) large.
Once it's full, a new buffer of (f->nsubf+DSUBF)*sizeof *subf
(newsize) is mallocated. Unfortunately memmove() reads (newsize)
bytes from the original (oldsize) buffer, causing a buffer overflow.
By switching to realloc(), we don't need to do buffer size calculation,
memmoving, and freeing of the original buffer.
Change-Id: Ibf85bc06abe1c8275b11acb1d7d346a14291d2cd
Reviewed-on: https://plan9port-review.googlesource.com/1520
Reviewed-by: Gleydson Soares <gsoares@gmail.com>
