speed up booting by implementing realloc+padovan

src/runtime/c/pgf/vector.cxx

@@ -0,0 +1,33 @@
+#include "data.h"
+
+static
+uint8_t next_padovan_tbl[] =
+  {0,1,2,3,4,5
+  ,7,7
+  ,9,9
+  ,12,12,12
+  ,16,16,16,16
+  ,21,21,21,21,21
+  ,28,28,28,28,28,28,28
+  ,37,37,37,37,37,37,37,37,37
+  };
+
+PGF_INTERNAL size_t
+get_next_padovan(size_t min)
+{
+	if (min <= 37)
+		return next_padovan_tbl[min];
+
+	size_t a = 49, b = 65, c = 86;
+	while (min > a) {
+		if (b < a) {
+			// overflow
+			throw pgf_systemerror(ENOMEM);
+		}
+		size_t tmp = a + b;
+		a = b;
+		b = c;
+		c = tmp;
+	}
+	return a;
+}