Add support for ELIXIR_HIDDEN, a regular expression that matches

applications in Elixir's lib and hides them from the actual code
path.

It will be used by ports to hide their own (already installed) files
in lib/ during the builds, and avoid unnecessary warnings.

lang/elixir/Makefile

@@ -4,6 +4,7 @@
 PORTNAME=	elixir
 PORTVERSION=	1.0.5
 DISTVERSIONPREFIX=	v
+PORTREVISION=	1
 CATEGORIES=	lang
 
 MAINTAINER=	olgeni@FreeBSD.org

lang/elixir/files/patch-bin_elixir

@@ -0,0 +1,20 @@
+--- bin/elixir.orig	2015-06-29 07:56:28 UTC
++++ bin/elixir
+@@ -97,4 +97,16 @@ if [ -z "$ERL_PATH" ]; then
+   fi
+ fi
+ 
+-exec "$ERL_PATH" -pa "$SCRIPT_PATH"/../lib/*/ebin $ELIXIR_ERL_OPTIONS $ERL -extra "$@"
++if [ -n "$ELIXIR_HIDDEN" ]; then
++  CODE_PATH=""
++
++  for lib in $(cd "$SCRIPT_PATH"/../lib/ && ls); do
++    if ! (echo "$lib" | grep -E "$ELIXIR_HIDDEN" >/dev/null 2>&1); then
++      CODE_PATH="$CODE_PATH "$SCRIPT_PATH"/../lib/$lib/ebin"
++    fi
++  done
++
++  exec "$ERL_PATH" -pa $CODE_PATH $ELIXIR_ERL_OPTIONS $ERL -extra "$@"
++else
++  exec "$ERL_PATH" -pa "$SCRIPT_PATH"/../lib/*/ebin $ELIXIR_ERL_OPTIONS $ERL -extra "$@"
++fi