allow multiple multiterms in top-level paramtext

[mengwong]

currently a paramtext can have multiple multiterm expressions

pt1.mt1  pt1.mt2  pt1.mt2

UNLESS the paramtext contains nested params:

pt1.mt1
         pt2.mt1  pt2.mt2

Then we can't say

pt1.mt1  pt1.mt2
         pt2.mt1  pt2.mt2

Why? Because there is currently some fussiness in the parser around needing to detect an EOL token.

But sometimes the EOL token is not available; instead we simply have a sameline situation. In the above, pt1.mt2 pt2.mt1 are returned as immediate adjacencies in the input token stream. So the parser needs to handle that edge case.

And related edge cases, where pt1.mt3 extends beyond pt2.mt.