[GRASS5] Backport of Tcl8.4 and FFTW3 to 6.0-CVS

Hi,

driven by the 6.0.2 patches in Debian I have backported
the Tcl8.4 and FFTW3 support to 6.0-CVS and run a
compilation which completed (even with strict compiler flags).

It will appear in 6.0.3.

Markus