FindPostgreSQL: automatically find installations from yum.postgresql.org

In commit v3.3.0-rc1~4^2 (FindPostgreSQL: Search some more common
packaging locations) the PostgreSQL_ADDITIONAL_SEARCH_PATHS variable was
removed. This was used e.g. by osm2pgsql to be able to build on CentOS
with recent PostgreSQL versions. At least add those locations from
yum.postgresql.org, which is a more or less official location.

Modules/FindPostgreSQL.cmake

@@ -88,8 +88,13 @@ foreach(suffix ${PostgreSQL_KNOWN_VERSIONS})
         "PostgreSQL/${suffix}/include/server")
   endif()
   if(UNIX)
+    list(APPEND PostgreSQL_LIBRARY_ADDITIONAL_SEARCH_SUFFIXES
+        "pgsql-${suffix}/lib")
+    list(APPEND PostgreSQL_INCLUDE_ADDITIONAL_SEARCH_SUFFIXES
+        "pgsql-${suffix}/include")
     list(APPEND PostgreSQL_TYPE_ADDITIONAL_SEARCH_SUFFIXES
-        "postgresql/${suffix}/server")
+        "postgresql/${suffix}/server"
+        "pgsql-${suffix}/include/server")
   endif()
 endforeach()