Changed second argument of calls to part_ok() and type_ok() from

Changed second argument of calls to part_ok() and type_ok() from
0 to 1, to match what store_multi() in mhstoresbr.c does.

A test case is below.  Without this fix, the following command:

  mhshow -part 1.1 -form mhl.null

produced no output.  mhlist showed a part 1.1:

 msg part  type/subtype              size description
1231       multipart/mixed            276
     1     multipart/related          107
     1.1   text/plain                  29

and "mhstore -part 1.1" properly stored it.  With this
fix, mhshow behaves properly and shows the part.

Analogous behavior happened with -type text/plain.

test case:

MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="NextPart_001"
Content-class: urn:content-classes:message
Date: Thu, 19 May 2011 00:00:00 -0000
From: sender@example.com
To: recipient@example.com

This is a multi-part message in MIME format.

--NextPart_001
Content-Type: multipart/related;
	type="multipart/alternative";
	boundary="NextPart_002"

--NextPart_002
Content-Type: text/plain;
	charset="utf-8"

This is the text/plain part.

--NextPart_002--

--NextPart_001--