Added "--strict" option to regression test scripts.
Revised tests to cover enhanced -gstrict-expr-width functionality.

Where possible (and where it doesn't change what is being tested),
tests have been tweaked to give the same results with or without
this option. Elsewhere, either the __ICARUS_UNSIZED__ pre-defined
macro has been used to adapt tests at compile time, or a variant
gold file has been provided. In many cases the gold file previously
created for the "vstd" version could be used.
Added param-extend test and updated expected results.