Implement dlib_vector_length to calculate the euclidean distance of the vectors

It not use the 'length' native versions of dlib, due I have to convert the
array to the vector, which will take the same time, and then I will use the
native method.

tests/vector_length.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Basic tests for dlib_vector_length
+--SKIPIF--
+<?php if (!extension_loaded("pdlib")) print "skip"; ?>
+--FILE--
+<?php
+var_dump(dlib_vector_length([0.0, 0.0],       [1.0, 0.0]));
+var_dump(dlib_vector_length([0.0, 0.0, -1.0], [0.0, 0.0, 1.0]));
+var_dump(dlib_vector_length([0.0, 2.5,  1.0], [0.0, 1.0, 1.0]));
+?>
+--EXPECT--
+float(1)
+float(2)
+float(1.5)

tests/version.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Just test php extension version
+--SKIPIF--
+<?php if (!extension_loaded("pdlib")) print "skip"; ?>
+--FILE--
+<?php
+var_dump(phpversion('pdlib'));
+?>
+--EXPECT--
+string(5) "1.0.2"