doc cmdInput1 and dependent(1)

[wlammen]

fix description of cmdInput; improve that of cmdInput1 (version 1)

[wlammen]

I struggle with both doxygen features and invariants of metamath. Surprisingly (to me) the \a tag does not create a link, only (?) \ref does. Replaced the tag all over the place.
Then addToMemPool does not add a fully used block of memory to memUsedPool (in fact, it issues a bug message in this case), but pntrLet seems to be tolerant here. This is really confusing, and it forces me to adapt formerly written text accordingly.

[wlammen]

The goal of this PR is reached. This is a good point to commit it.
(Only doc changes, code is left as is)
The next goal is print2

[wlammen]

Thanks for the detailed review

[wlammen]

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