Log Message:
Update to version 1.12.21.

Pkgsrc changes:
 * Modify license to dual either gpl2 or gpl3.
 * Adjust BUILDLINK_API_DEPENDS settings from configure.ac.
 * Adjust PLIST to files now installed.
 * Add comments to the existing patches.

Upstream notable changes (see ChangeLog in source for details):
gnumeric 1.12.21:
   * ODS import/export fixes
   * XLSX import/export fixes

gnumeric 1.12.20:
   * ODF import/export fixes and enhancements.
   * XLSX import/export fixes and enhancements.

gnumeric 1.12.19:
   * (no noteworthy major changes)

gnumeric 1.12.18:
   * Workaround gtk+ api/abi breaks.

gnumeric 1.12.17:
   * xlsx import/export improvements.

gnumeric 1.12.16:
   * ODS import/export improvements

gnumeric 1.12.15:
   * ods/xlsx graph import fixes
   * ods import/export fixes

gnumeric 1.12.14:
   * Many fixes related to conditional formats.
   * Try to disable Ubuntu's non-working scroll bars.

gnumeric 1.12.13:
   * ods import/export export fixes.
   * xls import/export export fixes.

gnumeric 1.12.12:
   * Test suite improvements.
   * ods import/export improvements
   * xls import/export improvements
   * xlsx import/export improvements

gnumeric 1.12.11:
   * A problem with saving to Excel97 format was fixed.

gnumeric 1.12.10:
   * Accuracy improvements
   * Work around gtk+ abi breaks
   * Win32 improvements