Postgresql version upgrades

[dmacks]

Building off PR #697, we have six different postgresql version suites. Here's a list of the oldest ones' reverse-deps on the 10.13 dist in case anyone has a hankerin' to do some upgrades:

postgresql94

• [x] grass64* (#830)
• [x] php5/libapache2-mod-php5
• [x] pvpgn-pgsql
• [x] root5* (#727)

varianted other packages for pg94

• [x] iplike-pg94
• [x] libdbi-drivers-pgsql94
• [ ] postgis94
• [ ] postgis94-java

postgresql95 [nothing]

varianted other packages for pg95

• [x] iplike-pg95
• [ ] postgis95
• [ ] postgis95-java

postgresql96

• [x] database-oct364 database-oct382
• [x] emboss*
• [x] gdal-pgsql
• [x] gdal2 (#697)
• [x] grass70* (deleted)
• [x] grass72* (#830)
• [x] libaprutil.0-postgresql
• [x] qgis218-py27
• [x] saga
• [x] tora

varianted other packages for pg96

• [x] iplike-pg96
• [ ] postgis96
• [ ] postgis96-java

postgresql10

• [x] psycopg2-pyXX

varianted other packages for pg10

• [ ] postgis10

postgresql11 [nothing]

varianted other packages for pg11

• [ ] postgis11

iplike-pg have no reverse-depends, but only has variants for 94/95/96 (not the newer 10/11/12) postgis has reverse-depends:gdal/gdal2, so migrating those is not more work, but only has variants for 94/95/96 (not the newer 10/11/12; ; should also upgrade postgis libgeos dep)

[dmacks]

Old-libversion gdal has a -pgsql variant that needs a postgresqlXX -dev/-shlibs and a version-matched postgisXX. It's currently at pg96, and that's the latest version of pg that the old version of postgisXX supports.

Newer versions of postgisXX (pg11+) have a dependency on gdal2 -dev/-shlibs. Neither version of gdal seems to have autodetection of postgis (just postgresql), so maybe it's a plugin and could be reduced to Recommends to break the dependency cycle if we wanted to upgrade gdal (old) to a newer pg version.

[dmacks]

libdbi-drivers-pgXX seems to be a mutually-exclusive set (maybe should not be varianted?)

[dmacks]

iplike now has a pg12 variant. Its only reverse-depends is opennms, where it is pg-version-agnostic, and opennms is only available for 10.9-10.11 (no idea why). So I'm turning off pg94/pg95/pg96 of it (would be trivial to re-add any older if someone actually wanted).

[dmacks]

gdal now uses postgis12, so we could turn off older postgisXX, which would leave all postgresql prior to 12 completely unused. phew.