Firebird 2.0.x branch with four months changes in review

Alex Peshkoff backported fix for CORE-3736: WITH LOCK clause is allowed for users with read-only rights on some table, thus blocking others from updating this table.
Dimitr backported CORE-3730: isc_dsql_exec_immed2() loses input parameter value with RETURNING clause.
And then he updated the docs for 2.0.7 release
Horsun Vlad backported fix for bug CORE-2977 that was in Firebird 2.1.x incorrectly works with indexed fields of type DATE in OLD ODS (9.1).
Paul Beach made modifications in 2.0.7 so it can be compiled and build on OSX.
Paul Reeves synced 2.0.7 branch with B2_0_Release.
In the end Paul Beach made in the conf. parameter DummyPacketInterval more accurate.