Drop guilegh interface

All of guile's interface files now use the scm interface.
This should not affect any users. Swig generated code
using the scm interface can be mixed with gh interface
using user code.
It does simplify maintenance of the guile swig code though.

Lib/guile/guile_scm.swg

@@ -10,7 +10,6 @@
 %runtime "swigrun.swg"       // Common C API type-checking code
 
 %runtime "guile_scm_run.swg"
-%include <ghinterface.i>
 %include <guile.i>
 
 %runtime %{
@@ -32,10 +31,6 @@
       else									\
             gswig_result = scm_append(scm_listify(gswig_result, scm_listify(object, SCM_UNDEFINED), SCM_UNDEFINED));		\
     }
-    /* used by Lib/exception.i */
-    #define gh_symbol2scm scm_str2symbol
-    /* useb by Lib/cdata.i */
-    #define gh_str2scm scm_mem2string
 
 %}