Add a .pragma directive for configuration files

Add a .pragma directive for configuration files

Currently added pragma:

.pragma dollarid:on

This allows dollar signs to be a keyword character unless it's
followed by a opening brace or parenthesis.

Fixes #8207

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8882)