This release restores compatibility with xserver-1.14 by removing
mibstore.h includes and miInitializeBackingStore() functions.
Since Nov.2010 (commit c4c4676) the only purpose of mibstore.h
was to define an empty function for backward compatibility.
Build helpers migrate to contemporary [build-aux] and [m4].
VALIDATION PLATFORM
* Debian (X server 1.14.3) on FIC ION603A (Geode LX800).
Signed-off-by: Martin-Éric Racine <martin-eric.racine@iki.fi>