Re: windows build slow due to windows.h includes

Hi,

For the AIO stuff I needed to build postgres for windows. And I was a bit
horrified by the long compile times. At first I was ready to blame the MS
compiler for being slow, until I noticed that using mingw gcc from linux to
cross compile to windows is also a *lot* slower than building for linux.

I found some blog-post-documented-only compiler flags [1], most importantly
/d1reportTime. Which shows that the include processing of postgres.h takes
0.6s [2]

Basically all the time in a debug windows build is spent parsing windows.h and
related headers. Argh.

The amount of stuff we include in win32_port.h and declare is pretty absurd
imo. There's really no need to expose the whole backend to all of it. Most of
it should just be needed in a few port/ files and a few select users.

But that's too much work for my taste. As it turns out there's a partial
solution to windows.h being just so damn big, the delightfully named
WIN32_LEAN_AND_MEAN.