Fix issue #318: test failures when cchardet is installed

feedparser imports cchardet or chardet depending on what's installed:
https://github.com/kurtmckee/feedparser/blob/11990ea1d8791acc76c67781f1d2011daf0c3a99/feedparser/encodings.py#L37-L40

Although these libraries are mostly equivalent, they return slightly different
encoding strings, even though both are correct and lead to succesful decoding.
This change allows the tests to be run with either library by accepting both
encoding names as correct.

tests/illformed/chardet/big5.xml

@@ -1,8 +1,8 @@
 <!--
 SkipUnless:   __import__('chardet')
 Description:  Big5 with no encoding information
-Expect:       bozo and encoding == 'Big5'
+Expect:       bozo and encoding in ('Big5', 'BIG5')
 -->
 <feed xmlns="http://www.w3.org/2005/Atom">
 <title>我希望??很容易?其翻?成中文，并有助于改??件。 感?您??本文。</title>
-</feed>
+</feed>

tests/illformed/chardet/euckr.xml

@@ -1,7 +1,7 @@
 <!--
 SkipUnless:   __import__('chardet')
 Description:  EUC-KR with no encoding information
-Expect:       bozo and encoding == 'EUC-KR'
+Expect:       bozo and encoding in ('EUC-KR', 'UHC')
 -->
 <rss>
 <channel>
@@ -10,4 +10,4 @@ Expect:       bozo and encoding == 'EUC-KR'
 <description>TypeKey 시스템이 UTF-8로 돌아가는데, 거기서 한글로 된 닉네임을 정할 경우에, EUC-KR로 된 무버블타입 블록에선 리다이렉트되어 전송되어오는 닉네임이 UTF라 당연히 깨어져 나타난다. 실제 블록 등에서 사용하는 필명 내지는 닉네임은 한글로 사용하는 많은 분들도 타입키에서의 닉네임은 이런 문제때문에 울며겨자먹기로 영어로 짓고 있다....</description>
 </item>
 </channel>
-</rss>
+</rss>

tests/illformed/chardet/gb2312.xml

@@ -1,7 +1,7 @@
 <!--
 SkipUnless:   __import__('chardet')
 Description:  GB2312 with no encoding information
-Expect:       bozo and encoding == 'GB2312'
+Expect:       bozo and encoding in ('GB2312', 'GB18030')
 -->
 <rss>
 <channel>

tests/illformed/chardet/windows1255.xml

@@ -1,7 +1,7 @@
 <!--
 SkipUnless:   __import__('chardet')
 Description:  windows-1255 with no encoding information
-Expect:       bozo and encoding == 'windows-1255'
+Expect:       bozo and encoding in ('windows-1255', 'WINDOWS-1255')
 -->
 <rss>
 <channel>