commctrl.h: Add WC_STATIC

[Felix Nawothnig]

Mike McCormack wrote:
>> I'm curious, what is the reason for the special case handling for MSVC 
>> and GCC when we have to do the portable way anyway?
> I can see two reasons:
> 
> * The portable way adds a (non-standard) symbol.

This could be fixed by adding a _ prefix.

> * The static string declaration may not be discarded by some compilers, 
> so it may needlessly increase the size of our binaries.

Unless MSVC or GCC do not do this optimization (and I'm sure both do) 
this is no argument.

Actually those 2 non-standard ways put additional burden on the 
optimizer - if one of those wide string literals is used multiple times 
the optimizer has to make sure that the compiler doesn't generate a copy 
for each reference (and I'm not so sure if GCC / MSVC do this, 
especially since writeable strings (yea, it's const but still) were only 
recently forbidden by GCC and I guess they are allowed in MSVC).

Felix