Custom Field and Post-Type names should be case insensitive

What steps will reproduce the problem? (Be specific enough so that someone
else can make the plugin fail for themselves. Remember: if the issue can't
be fixed if it can't be reproduced!)
1. Create a custom field named "MYFIELD"
2. Create another custom field named "myfield"

What is the expected output? What do you see instead?

I expect the 2nd instance to be invalid because the name is already taken.
However, the two variations of the names are allowed because the cases do not 
match.  This could be problematic because MySQL is case-insensitive in its 
searches.

*SYSTEM INFO* 
------------------------ 
Plugin Version: 0.9.7-dev
WordPress Version: 3.5
PHP Version: 5.3.2
MySQL Version: 5.1.44
Server OS: Darwin
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ACTIVE PLUGINS: 
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CURRENT THEME: Twenty Ten v.1.4 http://wordpress.org/

Original issue reported on code.google.com by ever...@fireproofsocks.com on 2 Jan 2013 at 7:12

google-code-export / wordpress-custom-content-type-manager

Custom Field and Post-Type names should be case insensitive #440