but rather use the "thread_id" counter.

Fixes bug#27078:
Compile error: lib_sql.cc cast from 'THD*' to 'pthread_t' loses precision


libmysqld/lib_sql.cc:
  Avoid casting a pointer to a (possibly) int, which will not compile on some platforms:
  Do not use the "thd" pointer to identify a thread in the embedded lib,
  but rather use the "thread_id" counter.
  
  Patch is proposed by Monty.  Fixes bug#27078.