add cmake support for POSTGIS_HAS_SERVER_VERSION (#4675)
fix memory crashes in getfeaturinfo requests (#4684)
variable declaration
add support for SVG symbology in cmake build (#4634)

note that svg-cairo does not properly link against current versions
of cairo as it uses an obsolete API. Support for SVG symbols is
disabled by default because of this
run simple svg tests on CI build
fix some compiler warnings