Search for version-numbered tclsh?

I notice that the recent patch to enforce finding a tclsh broke a couple
of buildfarm machines. On reflection, I remember that recent Tcl
versions don't automatically create a 'tclsh' symlink, only a
version-numbered program such as 'tclsh8.3'. I suggest that maybe we
ought to allow that without forcing people to set TCLSH manually.
Perhaps have PGAC_PATH_TCLSH do

AC_PATH_PROGS(TCLSH, [tclsh tcl tclsh8.5 tclsh8.4 tclsh8.3])

or some such.

regards, tom lane