compiler: Pass location to fatal_error.

The GCC function is changing.

The error functions need to move to a compiler-indepent
approach so that changes to the GCC functions are not a
concern here.

From-SVN: r220292

gcc/go/gofrontend/go.cc

@@ -63,7 +63,8 @@ go_parse_input_files(const char** filenames, unsigned int filename_count,
 	{
 	  file = fopen(filename, "r");
 	  if (file == NULL)
-	    fatal_error("cannot open %s: %m", filename);
+	    fatal_error(Linemap::unknown_location(),
+			"cannot open %s: %m", filename);
 	}
 
       Lex lexer(filename, file, ::gogo->linemap());