[PATCH] support: Implement support_quote_string

[Jonathan Nieder]

Florian Weimer wrote:

> 2018-11-27  Florian Weimer  <fweimer@redhat.com>
>
> 	* support/support.h (support_quote_string): Declare.
> 	* support/support_quote_string.c: New file.
> 	* support/tst-support_quote_string.c: Likewise.
> 	* support/Makefile (libsupport-routines): Add
> 	support_quote_string.
> 	(tests): Add tst-support_quote_string.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Thanks.