X11/Xlib.h defines Bool as a macro, which clashes with Reactor's Bool
class. This X11 header is also included by vulkan.h, vk_icd.h, and
EGL/eglplatform.h

Previously we undefined Bool in various places. It's not possible to
just undefine it in Reactor.hpp because one can have headers following
the inclusion of Reactor.hpp which redefine it (note our convention is
to include platform headers after project headers).

Since X11 is only needed in select places related to the windowing
system, we can instead avoid the use of these headers in other headers,
and only include them in .cpp files where necessary. Note that
vulkan_core.h contains the whole plaform-independent Vulkan API, so it
should be used instead of vulkan.h for all non-WSI code.

Bug: b/127920555
Change-Id: Id11a1c58b87802fe9e530387831693e44accae2b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/46368
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>