Update pragma rewiring expectations

[ecpeterson]

The quilc PR quil-lang/quilc#159 changes how rewirings get announced to the user: since the rewirings themselves are not considered to be machine-readable, it emits them as comments on existing instructions rather than as distinct instructions in their own right. This breaks some expectations that the pyQuil tests have, which this PR addresses.

Additionally, pyQuil's ANTLR grammar for Quil did not permit comments to be preceded by a substantial amount of whitespace. This PR additionally makes this permissiveness change.

[stevenheidel]

Neither of these changes make sense to me - do you have examples?

[ecpeterson]

Sure. Typical quilc output will soon look like this:

RZ(-1.500635301883098) 0                # Entering rewiring: #(0 1 2 3)
RZ(-pi/2) 2
HALT                                    # Exiting rewiring: #(0 1 2 3)

The current ANTLR grammar barfs on the spaces (or, perhaps, tabs) intervening between the instruction and the comment, and the test wants there to be specific PRAGMA instructions set aside for recording the rewirings, where there soon won't be any.

[karalekas]

LGTM