[could someone explain what, and why, tcl hash table was changed during an 8.x series?]
Michael Cleverly reports on comp.lang.tcl:
#if (TCL_MAJOR_VERSION == 8) && (TCL_MINOR_VERSION >= 4) #define Tcl_InitHashTableEx(x, y, z) Tcl_InitCustomHashTable(x, y, z) #endif
was needed to compile Ck.