Add MariaDB Connector/C as a built-in alternative (v3.2.3).

vendor/MDBC/plugins/auth/ref10/ge_p3_tobytes.c

@@ -0,0 +1,14 @@
+#include "ge.h"
+
+void ge_p3_tobytes(unsigned char *s,const ge_p3 *h)
+{
+  fe recip;
+  fe x;
+  fe y;
+
+  fe_invert(recip,h->Z);
+  fe_mul(x,h->X,recip);
+  fe_mul(y,h->Y,recip);
+  fe_tobytes(s,y);
+  s[31] ^= fe_isnegative(x) << 7;
+}