Gustaf,
I just tried to compile thread 2.6.1 with the command:
sudo ../configure --enable-threads \
--prefix=/usr/local/aolserver \
--exec-prefix=/usr/local/aolserver \
--with-aolserver=/usr/local/aolserver
as specified in your documentation, and got the following error:
checking for correct TEA configuration... ok (TEA 3.1)
checking for Tcl configuration... configure: WARNING: "Cannot find Tcl configuration definitions"
Turns out that you need to specify the location of TCL. Would you be able to update your documentation with the --with-tcl flag, as follows:
sudo ../configure --enable-threads \
--prefix=/usr/local/aolserver \
--exec-prefix=/usr/local/aolserver \
--with-aolserver=/usr/local/aolserver \
--with-tcl=/usr/lib/tcl8.4