Unbreak lang/gforth on i386

Hi Jasper, ports,

Here is a tiny diff that removes the BROKEN status for gforth on i386.

It builds with clang 6.0.0.

Testing:

- "make test" passes
- It has no consumers
- Tried many examples from Rosetta Code without issues

Charlène.

Index: Makefile
===================================================================
RCS file: /cvs/ports/lang/gforth/Makefile,v
retrieving revision 1.23
diff -u -p -r1.23 Makefile
--- Makefile 30 May 2018 11:29:29 -0000 1.23
+++ Makefile 6 Oct 2018 21:18:01 -0000
@@ -2,8 +2,6 @@

ONLY_FOR_ARCHS = amd64 i386 mips64 mips64el powerpc sparc64

-BROKEN-i386 = clang 5.0.0 ICE
-
USE_WXNEEDED = Yes

COMMENT = ANSI/200x Forth interpreter and compiler