Fall back to DejaVu instead of Vera, and fix serif italic filename.

It's not clear to me whether there used to be a serif oblique font which
has been superceded by the italic version, or whether the DejaVu filenames
have been broken since their inception and just were never fully tested.
Hopefully the latter.

Experimental/freetype/xrender-fonts.lisp

@@ -346,7 +346,7 @@
     ((:FIX (:ITALIC :BOLD)) . "DejaVuSansMono-BoldOblique.ttf") 
     ((:FIX :BOLD) . "DejaVuSansMono-Bold.ttf")
     ((:SERIF :ROMAN) . "DejaVuSerif.ttf") 
-    ((:SERIF :ITALIC) . "DejaVuSerif-Oblique.ttf")
+    ((:SERIF :ITALIC) . "DejaVuSerif-Italic.ttf")
     ((:SERIF (:BOLD :ITALIC)) . "DejaVuSerif-BoldOblique.ttf")
     ((:SERIF (:ITALIC :BOLD)) . "DejaVuSerif-BoldOblique.ttf") 
     ((:SERIF :BOLD) . "DejaVuSerif-Bold.ttf")
@@ -356,7 +356,7 @@
     ((:SANS-SERIF (:ITALIC :BOLD)) . "DejaVuSans-BoldOblique.ttf")
     ((:SANS-SERIF :BOLD) . "DejaVuSans-Bold.ttf")))
 
-(defvar *families/faces* *vera-families/faces*)
+(defparameter *families/faces* *dejavu-families/faces*)
 
 (defparameter *truetype-font-path* #p"/usr/share/fonts/truetype/ttf-dejavu/")