Follow default mysql version change.
Update to 2.21

Changelog:
SeaMonkey-specific changes

    Implemented an option to thread messages received by date.
    Allowed deletion of news posts by default.
    Implemented optional taskbar preview-per-tab.
    Added support (permission prompt) for desktop notifications.
    Added Isn't operator for searching by Priority.
    See the changes page for a more complete overview.

Mozilla platform changes

    Support for new scrollbar style on Mac OS X 10.7 and newer.
    Accessibility related improvements on using pinned tabs (bug 577727).
    Major SVG rendering improvements around Image tiling and scaling (bug 600207).
    Removed support for sherlock files that are loaded from application or profile directory.
    Support for W3C touch events disabled (bug 888304).
    Fixed several stability issues.

Fixed in SeaMonkey 2.21
MFSA 2013-92 GC hazard with default compartments and frame chain restoration
MFSA 2013-91 User-defined properties on DOM proxies get the wrong "this" object
MFSA 2013-90 Memory corruption involving scrolling
MFSA 2013-89 Buffer overflow with multi-column, lists, and floats
MFSA 2013-88 compartment mismatch re-attaching XBL-backed nodes
MFSA 2013-85 Uninitialized data in IonMonkey
MFSA 2013-83 Mozilla Updater does not lock MAR file after signature verification
MFSA 2013-82 Calling scope for new Javascript objects can lead to memory corruption
MFSA 2013-81 Use-after-free with select element
MFSA 2013-80 NativeKey continues handling key messages after widget is destroyed
MFSA 2013-79 Use-after-free in Animation Manager during stylesheet cloning
MFSA 2013-78 Integer overflow in ANGLE library
MFSA 2013-77 Improper state in HTML5 Tree Builder with templates
MFSA 2013-76 Miscellaneous memory safety hazards (rv:24.0 / rv:17.0.9)
Updated www/seamonkey to 2.21
Update to 2.21

* Sync with seamonkey-2.21
Updated www/seamonkey-l10n to 2.21