Question about compiling GTK app under Windows

[Dmitry Unruh <dmitryunruh googlemail com>]

Hello!
My name is Dmitry Unruh. I am a GTK programming beginner.
I downloaded GTK bundle for Windows and tried to compile experimental
application with command line: gcc -Wall -g exp.c -o exp.exe
%pkg-config --cflags gtk+-2.0%.
I use "#include <gtk/gtk.h>" line in source file.
I have received the message: gtk/gtk.h: No such file or directory.
I think the problem is in the path separator (/) which in Windows is "\".
When I corrected header file, my app was compilled.
Why GTK header files for Windows include non-Windows path separators?