Fix for GitHub issue #105 - fully support SV macro escape sequences.
Fix for GitHub issue #105 - fully support SV macro escape sequences.

The existing support for ``, `", and `\`" did not work in nested macro
definitions. Note that the new implementation only detects and replaces
these sequences inside the macro text (as required by the IEEE standard),
whereas the old implementation would detect and replace them anywhere in
the source files.

themperek/iverilog,themperek/iverilog,themperek/iverilog