Add code to make tarballs

* Imakefile (.PHONY): Add dist.
(dist, 12to11.tar.gz): New targets.

* README: Remove wayland-scanner dependency when not building
from a repository checkout.

Imakefile

@@ -119,7 +119,8 @@ $(OBJS): $(GENHEADERS)
 depend:: $(GENHEADERS) $(SRCS)
 
 cleandir::
-	$(RM) $(GENHEADERS) $(GENSRCS) transfer_atoms.h short_types.txt
+	$(RM) $(GENHEADERS) $(GENSRCS) transfer_atoms.h short_types.txt \
+	      12to11.tar.gz
 
 /* Undefine _BSD_SOURCE and _SVID_SOURCE, since both are deprecated
    and are also superseeded by _GNU_SOURCE.  */
@@ -127,3 +128,18 @@ cleandir::
 EXTRA_DEFINES := -D_GNU_SOURCE -U_BSD_SOURCE -U_SVID_SOURCE
 
 ComplexProgramTarget(12to11)
+
+.PHONY: dist
+dist: 12to11.tar.gz
+
+DIST_FILES = Imakefile $(SRCS) media_types.txt shaders.txt *.awk *.xml \
+  12to11.man README libraries.def *.h
+
+/* Include files generated by wayland-scanner, so the target does not
+   need to have it installed.  */
+
+12to11.tar.gz: $(DIST_FILES)
+	rm -rf 12to11.tar.gz
+	tar -cvf 12to11.tar $(DIST_FILES)
+	gzip 12to11.tar
+	$(RM) 12to11.tar

README

@@ -89,12 +89,14 @@ This directory is organized as follows:
                   those containing MIME types or shaders
 
 Building the source code is simple, provided that you have the
-necessary libwayland-server library, wayland-scanner, pixman, XCB, and
+necessary libwayland-server library, pixman, XCB, and X extension
-X extension libraries installed:
+libraries installed:
 
   xmkmf # to generate the Makefile
   make  # to build the binary
 
+wayland-scanner is also required when building from the repository.
+
 Running the binary should be simple as well:
 
   ./12to11