Document WESTON_VERSION_AT_LEAST() macro behavior

Adding this comment to explain the behavior:

  This macro may not do what you expect.  Weston doesn't guarantee any
  stable API between 1.X and 1.Y, and thus this macro will return
  FALSE on any WESTON_VERSION_AT_LEAST(1,X,0) if the actualy version
  is 1.Y.0 and X !=Y).  In particular, it fail if X < Y, that is,
  1.3.0 is considered to not be "at least" 1.4.0.

  If you want to test for the version number being 1.3.0 or above or
  maybe in a range (eg 1.2.0 to 1.4.0), just use the WESTON_VERSION_*
  defines above directly.

Version number testing is the one thing we can't break in the weston API,
so we'll have to settle for documenting the behavior and recommending
using the version number macros directly.

https://bugs.freedesktop.org/show_bug.cgi?id=74023
simple-egl: Fix -Wsign-compare compiler warning

Fixes the following compiler warning:

simple-egl.c:434:36: warning: comparison between signed and unsigned
integer expressions [-Wsign-compare]

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
input: Unlink saved kbd focus listener when releasing seat

Not doing this would leave a invalid list item in the view's destroy
signal listener list if destroying a seat that had previously lost
keyboard focus.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
build: Drop use of rsvg-convert

Just include the png in the repo.
compositor: Fix a couple of #includes to use "" instead of <>
clients: Drop pdf viewer sample client

This doesn't really add anything over the existing sample clients
and only complicates the build system with extra checks for poppler.
build: Use subdir-objects automake option

This makes automake place the object files in the same subdir as the
source file.  For a recursive build system as we have now, there's
no difference, but with a non-recursive build system it means that
the object files don't all end up in the toplevel directory.
build: Move data/Makefile.am into Makefile.am
build: Move wcap/Makefile.am into top-level Makefile.am
build: Move desktop-shell/Makefile.am into toplevel Makefile.am
build: Move xwayland/Makefile.am into toplevel Makefile.am
build: Move protocol/Makefile.am into toplevel Makefile.am
build: Move man/Makefile.am into toplevel Makefile.am
build: Move src/Makefile.am into toplevel Makefile.am
build: Move tests/Makefile.am into toplevel Makefile.am
build: Move clients/Makefile.am into toplevel Makefile.am
build: Move shared/Makefile.am into toplevel Makefile.am
build: Only regenerate src/git-version.h when .git/logs/HEAD changes

We rely on .git/logs/HEAD to be a file that changes when we commit to HEAD.
The first idea is to make the makefile rule depend on .git/HEAD, but that's
a symbolic ref that points to the current ref in refs/heads.  However,
.git/logs/HEAD changes whenever we commit to HEAD, so we can use that in the
makefile rule.
build: Drop wayland-scanner.mk

We now only have one Makefile.am so we don't need to keep these rules
in a separate file for sharing.
build: Stop using xmllint to validate protocol files

The scanner needs to be good enough.  If it crashes or fails to report
invalid input, that needs to get fixed.