Fix symbol export issue of prime_mod on Alpine bot

Apparently our gcc-6.4.0 on Alpine Linux distribution doesn't like defining static const
inside a method, lets put that on outside the classes.

src/hb-map-private.hh

@@ -39,6 +39,49 @@ inline uint32_t Hash (const T &v)
 }
 
 
+/* Following comment and table copied from glib. */
+/* Each table size has an associated prime modulo (the first prime
+ * lower than the table size) used to find the initial bucket. Probing
+ * then works modulo 2^n. The prime modulo is necessary to get a
+ * good distribution with poor hash functions.
+ */
+static const unsigned int prime_mod [] =
+{
+  1,          /* For 1 << 0 */
+  2,
+  3,
+  7,
+  13,
+  31,
+  61,
+  127,
+  251,
+  509,
+  1021,
+  2039,
+  4093,
+  8191,
+  16381,
+  32749,
+  65521,      /* For 1 << 16 */
+  131071,
+  262139,
+  524287,
+  1048573,
+  2097143,
+  4194301,
+  8388593,
+  16777213,
+  33554393,
+  67108859,
+  134217689,
+  268435399,
+  536870909,
+  1073741789,
+  2147483647  /* For 1 << 31 */
+};
+
+
 /*
  * hb_map_t
  */
@@ -184,52 +227,10 @@ struct hb_map_t
 
   protected:
 
-  static HB_INTERNAL inline unsigned int prime_for (unsigned int shift)
+  static inline unsigned int prime_for (unsigned int shift)
   {
-    /* Following comment and table copied from glib. */
-    /* Each table size has an associated prime modulo (the first prime
-     * lower than the table size) used to find the initial bucket. Probing
-     * then works modulo 2^n. The prime modulo is necessary to get a
-     * good distribution with poor hash functions.
-     */
-    static const unsigned int prime_mod [] =
-    {
-      1,          /* For 1 << 0 */
-      2,
-      3,
-      7,
-      13,
-      31,
-      61,
-      127,
-      251,
-      509,
-      1021,
-      2039,
-      4093,
-      8191,
-      16381,
-      32749,
-      65521,      /* For 1 << 16 */
-      131071,
-      262139,
-      524287,
-      1048573,
-      2097143,
-      4194301,
-      8388593,
-      16777213,
-      33554393,
-      67108859,
-      134217689,
-      268435399,
-      536870909,
-      1073741789,
-      2147483647  /* For 1 << 31 */
-    };
-
     if (unlikely (shift >= ARRAY_LENGTH (prime_mod)))
-      return prime_mod[ARRAY_LENGTH (prime_mod) -1];
+      return prime_mod[ARRAY_LENGTH (prime_mod) - 1];
 
     return prime_mod[shift];
   }