Compile with MSVS 2013 and fix compile error

[mike2718]

I had troble trouble when compiling with MSVS 2013, it says

main.c(103) : error C2065: 'F_OK' : undeclared identifier main.c(110) : error C2065: 'F_OK' : undeclared identifier main.c(112) : error C2065: 'F_OK' : undeclared identifier

So I made patches.

To compile, just do

nmake -f Makefile.msc

[jech]

That's clearly wrong. Please find where F_OK is defined, and include the right file in polipo.h.

[epu]

The F_OK is manually defined in mingw.h, for example. Maybe it should be moved out and shared between the 2 files that need it?