Work around subrs that block EXWM; other minor fixes

Some subrs (e.g. x-file-dialog) create X windows and block the execution of
EXWM, so they won't work normally.  This commit partly fixes this issue by
invoking them in a subordinate Emacs instance and trying to fetch the
result back.

* exwm.el (exwm-blocking-subrs): New variable for specify such subrs.
* exwm.el (exwm-enable, exwm--server-name, exwm--server-stop)
  (exwm--server-eval-at): The implementation.

* exwm-core.el:
* exwm-floating.el:
* exwm-layout.el:
* exwm-manage.el:
* exwm-randr.el:
  Evaluate constants at compile-time.

* README.md: Renamed from README.org to make the 'Commentary:' section
  used by GNU ELPA instead.

* exwm.el: Depends on XELB version 0.3.

1 files changed, 16 insertions, 0 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000000..09fe470d39
--- /dev/null
+++ b/README.md
@@ -0,0 +1,16 @@
+# Emacs X Window Manager
+
+EXWM (Emacs X Window Manager) is a full-featured tiling X window manager for
+Emacs built on top of [XELB](https://github.com/ch11ng/xelb).
+It features:
++ Fully keyboard-driven operation
++ Hybrid layout modes (tiling & stacking)
++ Workspace support
++ ICCCM/EWMH compliance
++ Basic RandR support (optional)
+
+Please check the [User Guide](https://github.com/ch11ng/exwm/wiki)
+for more details.
+
+**Note**: If you install EXWM from source, you need to manually install XELB
+(either from source or GNU ELPA).