Fix n and N formats, update tests.

example.php

@@ -11,6 +11,6 @@ var_dump(\danog\PHP\Struct::unpack("2cxbxBx?xhxHxixIxlxLxqxQxnxNxfxdx2sx5pP",
 
 )
 ));
-var_dump(\danog\PHP\Struct::unpack("<2s", danog\PHP\Struct::pack(">2s", "df")));
+var_dump(\danog\PHP\Struct::calcsize("n"));
 // 2c x b x B x ? x h x H x i x I x l x L x q x Q x n x N x f x d x 2s x
 //print(struct.unpack("2cxbxBx?xhxHxixIxlxLxqxQxnxNxfxdx2sx", struct.pack("2cxbxBx?xhxHxixIxlxLxqxQxnxNxfxdx2sx", "nv", 100, 100, False, 333, 444, 232423, 234342, 234234234234, 234234234234, 234234234234, 234234234234, 34434, 344434, 2.2343, 3.03424, "dd")));

lib/danog/PHP/Struct.php

@@ -49,8 +49,8 @@ class Struct {
 		$this->NATIVE_FORMATS = array_merge([
 			// These formats need to be modified after/before encoding/decoding.
 			"P" => $this->IS64BIT ? "Q" : "L", // integer or long integer, depending on the size needed to hold a pointer when it has been cast to an integer type. A NULL pointer will always be returned as the Python integer 0. When packing pointer-sized values, Python integer or long integer objects may be used. For example, the Alpha and Merced processors use 64-bit pointer values, meaning a Python long integer will be used to hold the pointer; other platforms use 32-bit pointers and will use a Python integer.
-			"n" => "i",
-			"N" => "I",
+			"n" => $this->IS64BIT ? "q" : "l",
+			"N" => $this->IS64BIT ? "Q" : "L",
 		], $this->FORMATS);
 		$this->SIZE = [
 			"p" => 1,