Bump bison baseline?

[Mike Kaganski]

Our builds emit these warnings:

> C:/cygwin64/home/tdf/jenkins/workspace/gerrit_windows/unoidl/source/sourceprovider-parser.y:13.1-12: 
> warning: deprecated directive: ‘%pure-parser’, use ‘%define 
> api.pure’ [-Wdeprecated]

(e.g., https://ci.libreoffice.org/job/gerrit_windows/201968/consoleFull)

The causing code is 
https://opengrok.libreoffice.org/xref/core/unoidl/source/sourceprovider-parser.y?r=23d7910c1e1fc41ab3b7b931cb91e007e09a4086&mo=418&fi=13#13

According to 
https://lists.gnu.org/archive/html/bug-bison/2019-06/msg00013.html , we 
better use `%define api.pure full`, available since bison 2.7.

According to 
https://packages.debian.org/search?keywords=bison&searchon=names&suite=all&section=all, 
Debian oldstable has bison 3.7.

Our configure requires at least version 2.0 ( 
https://opengrok.libreoffice.org/xref/core/configure.ac?r=e4b24dba07c54c1957df8c42a19392bd01fc01e2#12230 
), which seems quite old now.

Would bumping bison baseline, and replacing the problematic 
instruction,be OK at this time?


-- 

Best regards,

Mike Kaganski