fblangref50: document system packages in a new chapter #180
Description
In fblangref40, there is a single system package, RDB$TIME_ZONE_UTIL, which is documented as part of the Supplemental Time Zone Features section of the Data Types and Subtypes chapter. Firebird 5.0 introduces two additional system packages, RDB$PROFILER and RDB$BLOB_UTIL. It would be possible to document RDB$BLOB_UTIL in a similar way in section Binary Data Types, the same cannot be said for RDB$PROFILER. The information also doesn't fit in Built-in Scalar Functions (for one these aren't only functions, but also procedures, and those that are function aren't built-in functions as such).
Instead, a new chapter System Packages (or similar) needs to be added in fblangref50, where all three packages are to be documented.