Add devel/elixir-unsafe, an Elixir library to generate unsafe

bindings for functions (i.e. functions that can crash rather than
returning a tagged error value).

More background here:

  http://whitfin.io/generating-bang-functions-in-elixir/

devel/Makefile

@@ -542,6 +542,7 @@
     SUBDIR += elixir-tirexs
     SUBDIR += elixir-trailing_format_plug
     SUBDIR += elixir-tzdata
+    SUBDIR += elixir-unsafe
     SUBDIR += embb
     SUBDIR += epl.el
     SUBDIR += epm

devel/elixir-unsafe/Makefile

+# $FreeBSD$
+
+PORTNAME=	unsafe
+PORTVERSION=	1.0.0
+DISTVERSIONPREFIX=	v
+CATEGORIES=	devel
+PKGNAMEPREFIX=	elixir-
+
+MAINTAINER=	olgeni@FreeBSD.org
+COMMENT=	Generate unsafe bindings for Elixir functions
+
+LICENSE=	MIT
+
+USES=		elixir
+USE_GITHUB=	yes
+GH_ACCOUNT=	whitfin
+
+MIX_REWRITE=	yes
+
+.include <bsd.port.mk>

devel/elixir-unsafe/distinfo

+TIMESTAMP = 1525621894
+SHA256 (whitfin-unsafe-v1.0.0_GH0.tar.gz) = 8a5850f82bc7ff6ca9a3da88e11854e794a3342c7bed72e94bb4b9afe30e696f
+SIZE (whitfin-unsafe-v1.0.0_GH0.tar.gz) = 8013

devel/elixir-unsafe/pkg-descr

+This library is designed to generate unsafe bindings for Elixir
+function definitions at compile time.
+
+WWW: https://github.com/whitfin/unsafe

devel/elixir-unsafe/pkg-plist

+lib/elixir/lib/unsafe/ebin/Elixir.Unsafe.Compiler.beam
+lib/elixir/lib/unsafe/ebin/Elixir.Unsafe.Generator.beam
+lib/elixir/lib/unsafe/ebin/Elixir.Unsafe.beam
+lib/elixir/lib/unsafe/ebin/unsafe.app
+lib/elixir/lib/unsafe/lib/unsafe.ex
+lib/elixir/lib/unsafe/lib/unsafe/compiler.ex
+lib/elixir/lib/unsafe/lib/unsafe/generator.ex
+%%PORTDOCS%%%%DOCSDIR%%/README.md