Fix compiler warning

libscdl.h:24: warning: function declaration isn’t a prototype


git-svn-id: https://www.opensc-project.org/svnp/opensc/trunk@5245 c6295689-39f2-0310-b995-f0e70906c6a9

src/common/libscdl.h

@@ -21,4 +21,4 @@
 void *sc_dlopen(const char *filename);
 void *sc_dlsym(void *handle, const char *symbol);
 int sc_dlclose(void *handle);
-const char *sc_dlerror();
+const char *sc_dlerror(void);