Log Message:
libmatroska: updated to 1.5.2

Released v1.5.2:
* Build system: fixed symbol visibility issue causing linker
  failures since 1.5.1.

Released v1.5.1:
* Build system: libEBML 1.3.8 is now required.
* Build system: various fixes to the cmake rules regarding
  visibility, naming and building DLLs on Windows.
* KaxBlock: fixed a potential access to invalid memory due to
  invalid lace sizes read from invalid data.
* KaxBlock: fixed a potential null pointer dereference triggerable
  by reading invalid data.