Add 'image' type/extensions to wp_ext2type() and make it case insensitive

[xparham]

Well, I know that you can add any type check to wp_ext2type() with ext2type filter, but why it does not support image type by default?

On the other note, I think this function should be case insensitive when it searches for the extension in type arrays.

Please find a patch attached.

[SergeyBiryukov]

#25261 was marked as a duplicate.

[SergeyBiryukov]

I saw some issues on support forums where image uploading didn't work, and it's been reported that adding image types to wp_ext2type() fixes that (I even saw instructions for hacking core instead of using the ext2type filter).

I guess there's a plugin doing something weird, but looks like 25176.patch​ would solve that as well.

[ocean90]

In 25437:

Add 'image' type/extensions to wp_ext2type() and make it case insensitive. props xparham. fixes #25176.