Make (char*, size_t) typemap usable for strings of other types in Java.

Notably it now works for "unsigned char*" strings.

Add a test to check that it now works in Java and also showing that it already
worked for the other languages with support for this typemap.

Examples/test-suite/char_binary.i

@@ -5,12 +5,16 @@ A test case for testing non null terminated char pointers.
 %module char_binary
 
 %apply (char *STRING, size_t LENGTH) { (const char *str, size_t len) }
+%apply (char *STRING, size_t LENGTH) { (const unsigned char *str, size_t len) }
 
 %inline %{
 struct Test {
   size_t strlen(const char *str, size_t len) {
     return len;
   }
+  size_t ustrlen(const unsigned char *str, size_t len) {
+    return len;
+  }
 };
 
 typedef char namet[5];