Quil symbols and Quil.SI API

[ghost]

This is intended as a follow-on issue for the pending draft PR 'Draft: introduce cl-quil.si package, eliminate :: refs in Quilt #707'. A large number of symbols in the Quil package are exported. A fair number of internal symbols were recently added to the recently created Quil.SI package (expected to be included in Master in a forthcoming PR merge). The creation of the Quil.SI package itself was done mostly mechanically in order to avoid double colon (::) access to Quil-internal symbols.

Once the PR is merged, the symbols in Quil.SI should be reviewed, and it should be rationalized as to whether the access is in the spirit of the intended use of Quil.SI package, whether the symbol in question ought to have been exported from Quil to begin with, or whether some other change ought to have been done instead.