Log Message:
Update to 3.21.11.
 - build system improvements contributed by Michael Biebl - thx!
 - all patches from 3.20.5 (v3-stable) have been incorporated:
   - bugfix: potential abort with DA queue after high watermark is reached
     there exists a race condition that can lead to a segfault.
     Thanks go to vbernetr, who performed the analysis and provided patch,
     which I only tweaked a very little bit.
   - fixed bugs in RainerScript:
     - when converting a number and a string to a common type,
       both were actually converted to the other variable's type.
     - the value of rsCStrConvertToNumber() was miscalculated.
       Thanks to varmojfekoj for the patch
   - fixed a bug in configure.ac which resulted in problems
     with environment detection - thanks to Michael Biebl for the patch
   - fixed a potential segfault problem in gssapi code
     thanks to varmojfekoj for the patch
   - doc enhance: provide standard template for MySQL
     module and instructions on how to modify schema