Sqlcycli

Added `sqlfunc` module:
- `sqlfunc` module provides a collection of classes to represent the MySQL functions. Each class corresponds to a distinct MySQL function (e.g., TO_DAYS, MD5, etc.), and all of them derive from a common base class `<'SQLFunction'>`.
- The function classes in this module are more like a wrapper for the function values so the 'escape()' method in the 'sqlcycli' package can handle them correctly.

Updates: extended support for cytimes (2.0.0).

Minor performance updates to the transcode module.

Bugfix: remove unnecessary cdivision directives

Bugfix:
- escape for datetime.date now clamp by max ordinal.
- escape for datetime.datetime, np.datetime64 now clamp by min & max datetime microseconds.

Minor optimizations.