Read the SQL declarations without their comments

[estebanzimanyi]

The SQL signatures are read from the CREATE FUNCTION statements with every
-- and /* */ comment blanked first, newlines kept and string literals stepped
over, as parser/temporaltypes.py reads C. A statement commented out is no
declaration: the extension does not create it, so no binding may register
it. A commented line inside a declaration is no part of it:
asMVTGeom(tgeompoint, ...) keeps an older -- RETURNS tgeompoint above its
RETURNS geom_times, which left the statement without a return type.

Measured. Over MobilityDB a362004728 the catalog drops 6 signatures the
extension does not create, each commented out in its .in.sql:
stops(tgeometry, float, interval), stops(tgeography, float, interval),
stops(tjsonb, interval), tsample(trgeometry, interval, timestamptz),
bearing(tgeogpoint, tgeogpoint) and asMVTGeom(tgeometry, ...), and
asMVTGeom(tgeompoint, ...) returns geom_times, so tpoint_as_mvtgeom states
its sqlReturnType. The catalog is otherwise identical.

Witness. tests/test_sql_comments.py blanks line and nested block comments,
keeps a comment opener inside a literal, registers nothing for a declaration
commented out, and reads the return type and the arguments of a declaration
carrying commented lines.