Log Message:
expat: updated to 2.6.1

Release 2.6.1

Bug fixes:
  Make tests independent of CPU speed, and thus more robust
  Expose billion laughs API with XML_DTD defined and
    XML_GE undefined, regression from 2.6.0

Other changes:
  Hide test-only code behind new internal macro
  Autotools: Reject expat_config.h.in defining SIZEOF_VOID_P
  Address compiler warnings
  Version info bumped from 10:0:9 (libexpat*.so.1.9.0)
     to 10:1:9 (libexpat*.so.1.9.1); see https://verbump.de/
     for what these numbers do

Infrastructure:
  CI: Adapt to breaking changes in clang-format