Move back IN_GCLIST flag into field tlflags, since thread list and gc list still share same lock.
Move back IN_GCLIST flag into field tlflags, since thread list and gc list
still share same lock.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase