[Stackless] Building Boost::Stackless_Python - undefined symbol: PyUnicodeUCS4_FromEncodedObject

[Simon Pickles]

Checking my config.log after ./configure --use-unicode=ucs4, I wondered 
if this was relevant:

configure:20053: checking size of wchar_t
configure:20361: gcc -pthread -o conftest -g -O2   conftest.c -lpthread 
-ldl  -lutil >&5
configure:20364: $? = 0
configure:20370: ./conftest
configure:20373: $? = 0
configure:20396: result: 4
configure:20408: checking for UCS-4 tcl
configure:20436: gcc -pthread -c -g -O2  conftest.c >&5
conftest.c:212:17: error: tcl.h: No such file or directory
conftest.c:214:3: error: #error "NOT UCS4_TCL"
configure:20442: $? = 1
configure: failed program was:
| /* confdefs.h.  */