[DynInst_API:] [dyninst/dyninst] ec646c: Fix compilation of thread_db_process

[Sasha NÃcolas <noreply@xxxxxxxxxx>]

  Branch: refs/heads/fix-thread_db_process
  Home:   https://github.com/dyninst/dyninst
  Commit: ec646c0aff921378c8f48f337dea50ca7f6d1683
      https://github.com/dyninst/dyninst/commit/ec646c0aff921378c8f48f337dea50ca7f6d1683
  Author: Sasha Nicolas <sasha@xxxxxxxxxxx>
  Date:   2019-03-26 (Tue, 26 Mar 2019)

  Changed paths:
    M proccontrol/src/int_thread_db.C
    M proccontrol/src/int_thread_db.h

  Log Message:
  -----------
  Fix compilation of thread_db_process
On a machine without libthread_db.so, the placeholder class
had missing member functions and the contructors were calling
wrong base constructors.