[driver, doc] Support escaping special characters in specs

[Sandra Loosemore]

On 01/16/2017 03:54 AM, Rainer Orth wrote:
> Hi Sandra,
>
>> On 01/13/2017 05:59 AM, Rainer Orth wrote:
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -26391,6 +26391,13 @@ be as many clauses as you need.  This ma
>>>
>>>   @end table
>>>
>>> +The switch matching text @code{S} in a %@{@code{S}@},
>>> +%@{@code{S}:@code{X}@} or similar construct can use a backslash to
>>> +ignore the special meaning of the character following it, thus allowing
>>> +literal matching of a character that is otherwise specially treated.
>>> +For example, %@{@code{std=iso9899\:1999}:@code{X}@} would substitute
>>> +@code{X} if the @option{-std=iso9899:1999} option were given.
>>> +
>>
>> I see this "%@{@code{..." markup appears in the paragraph just before this,
>> but it's wrong.  The whole thing needs to be wrapped in @samp and the
>> nested @codes removed, like
>>
>> s/%@{@code{S}:@code{X}@}/@samp{%@{S:X@}}/
>>
>> etc.
>
> I see, fixed.  I assume this applies to the uses inside @item, too, and
> irrespective of %{S:X} or %{S}?

It looked to me like this table environment uses

@table @code

so there should be no need for additional @code markup within the @item 
tags.

I'm not asking you to repair existing bad markup elsewhere in this 
section, just not propagate it to your new paragraph of text.

-Sandra