bug#22765: Missing interfaces for syntax of characters in buffers.

[Alan Mackenzie]

Hello, Emacs.

In all versions of Emacs to date, we are missing an interface to return
the syntax of a character in a buffer in a "nice" form.  By a "nice"
form, I mean the characters ?\ , ?., ?w, ?\(, ?\), etc., which programs
should be able to use.

We have `char-syntax', but that takes no account of syntax-table text
properties which might be on a buffer position, and so shouldn't really
be used any more in buffers.  There are still around 160 uses of
`char-syntax' in our sources.

We have `syntax-after', but this returns a raw syntax descriptor (like
(4 . 41)), and we have no means of extracting ?\( from this.

I propose adding the two functions `syntax-class-to-char' which would
convert 4 to ?\(, and `char-syntax-after', which would return ?\(
directly, given a buffer position with such a character under it.

This would greatly aid in the conversion of these old `char-syntax'
calls.

-- 
Alan Mackenzie (Nuremberg, Germany).