Log Message:
Update cad/verilog (icarus verilog) from 0.9.7 to 10.1.1

pkgsrc changes:
 - note GitHub tags (but not use them for now)
 - remove conflict with nonexistent verilog-current
 - install additional documentation in share/doc/ivl (not share/ivl)
 - drop DESTDIR gymnastics - build works without it
 - (re)enable gperf dependency
 - regenerate buildlink3.mk
 - drop patches/patch-lexor_keyword.cc - no longer needed
 - patches/patch-vpi_Makefile partially fixed upstream - rest not needed

upstream changelog
==================

Probably the only notes available:

Here are the release notes for Icarus Verilog release branch 10. The 10
release is a huge improvement over the 0.9 release series, in every
aspect. Much more of the Verilog and SystemVerilog language is supported,
many bugs have been fixed, and performance has improved. The changes
(improvements!) are so numerous that there is no point attempting to
enumerate them.

 -- http://iverilog.wikia.com/wiki/Release_Notes_Icarus_Verilog_10