Missing structures and equations in headers?

I am using fasm 1.68 windows version.
I find some definations of structures or symbols are missing.
For example, the SEH related structures are not included; and some WM_XXX values like:

Code:

WM_GETHOTKEY                 = 0033h
WM_GETOBJECT              = 003Dh
WM_OTHERWINDOWCREATED     = 0x0042
WM_SYNCPAINT  = 0x0088

are also missing.

So, when I encounter an undefined stuff, I have to search for it by myself. Although it's not a very hard work, it is really time consuming.

My questions:
1) Does fasm have any intentions to keep maintaining these headers (I mean completing the missing stuff)?
2) How do you guys deal with these undefined stuff when programming in assembly language? Keep collecting informations from C headers or using some other packages like masm32?

Thanks.