improve the help message about psql -F

in the offical doc,-F say：

> Use separator as the field separator for unaligned output.

but in the psql --help,-F say:

> set field separator (default: "|")

if user don't read the offical doc carefully,he can use:

psql -F , -c 'select ...'

But can't get what he want.
It is a bad user Experience.

I make a patch change the help message for -F to:

> set field separator for unaligned output (default: "|")

patch for head attached.

Jov
blog: http:amutu.com/blog <http://amutu.com/blog>