textsearch: doc - fix spelling in lib/textsearch.c.

Found the following spelling errors while reading the textsearch code:
  "facitilies"  -> "facilities"
  "continously" -> "continuously"
  "arbitary"    -> "arbitrary"
  "patern"      -> "pattern"
  "occurences"  -> "occurrences"

I'll try to push this patch through DaveM, given the only users
of textsearch is in the net/ tree (nf_conntrack_amanda.c, xt_string.c
and em_text.c)

Signed-off-by: Jesper Sander <sander.contrib@gmail.com>
Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>