Log Message:
xa: update to 2.3.11.

ChangeLog:

  * Compilation fix for gcc 10 (thanks Dan Horak).
  * Allow pointer arithmetic in relocating mode within the same segment, since
    the result is segmentless (thanks Andre for the report).
  * .dsb with negative quantities shouldn't work (thanks Andre for the report).
  * Stop a divide-by-zero floating point exception (thanks Frederic Cambus).
  * Testsuite expanded.