unicode: Support diacritic marks > 0xffff (disabled for now)

* Terminating record of the max unicode codepoint (0x10ffff)
 * Add in Arabic diacritic marks in the 0x10efa..10efff range

This is currently disasbled due to it effectively doubling the
size of our diacritic table. The diacritics added are unlikely
to be seen in practice as they are used only in some formal
Quaranic contexts.  If we identify other diacritic marks above
0xffff, then we can turn this code on.

Change-Id: I50c2eace18c70be6fe7199fccab190e7da401089

firmware/common/diacritic.c

@@ -34,12 +34,20 @@
 /* Each diac_range_ struct defines a Unicode range that begins with
  * N diacritic characters, and continues with non-diacritic characters up to the
  * base of the next item in the array, [info] packs RTL status and the count of
- * diacritic chars after [base]. RTL occupies the MSB and CNT the (7) lower bits
+ * diacritic chars after [base]. RTL occupies the MSB and CNT the remaining bits
  */
 
+#ifdef UNICODE32
+//#define DIAC_UCSCHAR
+#endif
+
 struct diac_range
 {
-    uint16_t base; /* Not ucschar_t until we need >16b */
+#if defined(DIAC_UCSCHAR)
+    ucschar_t base;
+#else
+    uint16_t base;
+#endif
     uint16_t info; /* [RTL:1 CNT:15] */
 };
 
@@ -192,7 +200,13 @@ static const struct diac_range diac_ranges[] =
     DIAC_RANGE_ENTRY(0xfe20, 0xfe30, 0), /* v1.0 - v8.0 */
     DIAC_RANGE_ENTRY(0xfe70, 0xfe70, 1),
     DIAC_RANGE_ENTRY(0xff00, 0xff00, 0),
+    /* Final entry is a terminator */
+#if defined(UNICODE32) && defined(DIAC_UCSCHAR)
+    DIAC_RANGE_ENTRY(0x010efa, 0x010f00, 1),  /* v15.0 - v17.0 */
+    DIAC_RANGE_ENTRY(0x10ffff, 0xffff, 0),
+#else
     DIAC_RANGE_ENTRY(0xffff, 0xffff, 0),
+#endif
 };
 
 #define MRU_MAX_LEN 32