interp/params: do not require a named param to be defined when parsing a sub

this fixes	the second reported issue in
https://sourceforge.net/p/emc/bugs/315/, the following now parses OK:

O<multipass> SUB
#<sub> = #1
O#<sub> CALL
O<multipass> ENDSUB
m2
Merge remote branch 'origin/bug315-2-fix' into v2.5_branch
Test for bug 315 part 2
tests: use NO_FORCE_HOMING with the linuxcncrsh tests

The linuxcncrsh UI has no way to wait for homing to complete, short of
polling the emcstat structure.  Rather than do that (and rather than
reimplementing these tests in python) I'm setting [TRAJ]NO_FORCE_HOMING
so that the MDI commands may run whether or not the homing has happened.

Also, remove the now-superfluous homing steps from the tests.