add shDblParen to shLoopList to correctly highlight
arithmetic expressions for Bash and Ksh
This should allow code such as:
```bash
declare -i i j
for i in foo bar
do ((j = 1 << j))
done
```
Signed-off-by: Lucien Grondin <grondilu@yahoo.fr>
Signed-off-by: Christian Brabandt <cb@256bit.org>
a390e984db
