Consult compiled paramstyle on execute_compiled

Consult compiled paramstyle on execute_compiled

Fixed bug where in the unusual case of passing a
:class:`.Compiled` object directly to :meth:`.Connection.execute`,
the dialect with which the :class:`.Compiled` object were generated
was not consulted for the paramstyle of the string statement, instead
assuming it would match the dialect-level paramstyle, causing
mismatches to occur.

Change-Id: I114e4db2183fbb75bb7c0b0641f5a161855696ee
Fixes: #3938