Make cmake comments more consistent

Hello,

If you run 'cmake -LAH' in the source directory, you get a description of the cmake options, but the capitalisation of the descriptions are not consistent, making it hard to find the options you need.

For example, I was trying to find the option to disable compiling Mroonga, as it was causing problems during compile time on my machine. I ran the command above, and filtered for mroonga, groonga, [Gg]roonga, and it was only when I filtered for MROONGA that I found what I was looking for ('PLUGIN_MROONGA:STRING=DYNAMIC').

The entries in 'cmake -LAH' are as follows:

// How to build plugin MROONGA. Options are: NO STATIC DYNAMIC YES AUTO.

PLUGIN_MROONGA:STRING=DYNAMIC

If the description was: How to build plugin Mroonga..., I may have found it. Can this be updated?

Thanks.