Don't attempt to actually do double code removals

...that easily works around the problem that in a rewriter rewriting types of
VarDecls like

   T x, y;

it would try to replace T twice.  Also, keep the list of removals globally with
the (global) rewriter.

Change-Id: I55b8d11986c2a29e09ff40132fd114a0cc48dc90
Add SvStream::ReadCharAsBool

Change-Id: I9dc0525e04de5ae79205872b779dcd0115a9cc14