Fix bad slang modules file

The modules file had a few errors that prevented slang from being built.
First the src/elfobjs file needed to be created before make started.
Second it needed to be configured without external png, pcre and onig
libraries it doesn't need for this application.

modules/slang

@@ -11,6 +11,9 @@ slang_configure := ./configure \
 	--prefix "/" \
 	--host i386-elf-linux \
 	--with-png=no \
+	--with-pcre=no \
+	--with-onig=no \
+  && mkdir src/elfobjs
 
 slang_target := \
 	$(MAKE_JOBS) \