sci-electronics/iverilog: bump to 10.3

sci-electronics/iverilog: bump to 10.3

Bump iverilog version to 10.3

Follow these URL:
* http://iverilog.icarus.com
* https://github.com/steveicarus/iverilog
Update LICENSE to LGPL-2.1
Rewrite ebuild to download file from iverilog official github repo
Update maintainer list, add proxy-maint
Add github upstream https://github.com/steveicarus/iverilog
Bump the version with bugfixes
Replace autoconf.sh to make it utilize the autotools eclass
Fix upstream parallel compilation bug
Add https://github.com/steveicarus/iverilog in HOMEPAGE array
Happy new year 2020

Tested from my overlay:
https://github.com/vowstar/vowstar-overlay/

Closes: https://bugs.gentoo.org/687080
Closes: https://bugs.gentoo.org/701122
Closes: https://bugs.gentoo.org/704344
Package-Manager: Portage-2.3.82, Repoman-2.3.20
Signed-off-by: Huang Rui <vowstar@gmail.com>
Closes: https://github.com/gentoo/gentoo/pull/14096
Signed-off-by: Joonas Niilola <juippis@gentoo.org>