TabSRMM RichEdit50W, SpellChecker fix

Hi, @georgehazan 
I didn't think fork reset would also remove comments for my previous pull request, so sorry about that. My another try for same thing. :) (http://trac.miranda-ng.org/ticket/740)

I've changed TabSRMM richedits in message windows to `RichEdit50W` (and left `20W` in setting dialogs).
Which broke underlining in SpellChecker - I've fixed that using newer SDK header file for richedit.h. Which many people wouldn't have (with VS2010), so I copied it to sources... Not so nice solution, I know that.

I've noticed that there were some change of library in tabsrmm. `Msftedit.dll` is for 50W. http://trac.miranda-ng.org/changeset/7622

I've tested both on Win 7 64bit and Win XP SP3 32bit. Everything's ok. Again, it's up to you.

![ohsb](https://cloud.githubusercontent.com/assets/6796369/5087218/1c4bee4c-6f26-11e4-95b7-562b71bbd1c6.png)