bug#66660: [PATCH] Fix dns-mode-syntax-table

[Lassi Kortela]

> Could you provide an example of something which is incorrectly
> highlighted, briefly explain what is wrong before your patch, and what
> your patch does?  Thanks again.

Sure. Here is the DNS zone for the domain schemers.org:

https://raw.githubusercontent.com/schemeorg/schemeorg/master/dns/schemers.org.zone

On the following two lines, the text in double quotes was not
highlighted.

@ IN TXT "v=spf1 include:simplelists.com -all"

srfi IN TXT "v=spf1 include:simplelists.com -all"

On the following line, the part "k=rsa was not highlighted, and the
rest of the line ;p=MIGf[...]QAB" starting at the semicolon was
incorrectly highlighted as a comment instead of a string literal.

selector1._domainkey.srfi IN TXT "k=rsa;p=MIGf[...]QAB"

The patch causes the parts in double quotes to be highlighted as string 
literals. Since the part starting at the semicolon is inside a string, 
it is no longer incorrectly highlighted as a comment.

Motion commands such as forward-sexp are likewise fixed.