Optimize building djvulibre.

1. Don't build xmltools in the emulator
2. Remove duplicate --disable-desktopfiles
3. Don't build LFS support. The largest DjVu file I have ever published
was a highres facsimile edition of the London Walton Polyglot (1657)
which was a "mere" 1GB in size and I don't think anyone produced
anything bigger. Besides, storing DjVu files >2GB in size (even if
they existed, which I doubt) on a Kindle with only 3GB total storage
space is _exceedingly_ unlikely.

Makefile

@@ -189,9 +189,9 @@ $(MUPDFLIBS) $(THIRDPARTYLIBS): $(MUPDFDIR)/cmapdump.host $(MUPDFDIR)/fontdump.h
 $(DJVULIBS):
 	-mkdir $(DJVUDIR)/build
 ifdef EMULATE_READER
-	cd $(DJVUDIR)/build && ../configure --disable-desktopfiles --disable-shared --enable-static
+	cd $(DJVUDIR)/build && ../configure --disable-desktopfiles --disable-shared --enable-static --disable-xmltools --disable-largefiles
 else
-	cd $(DJVUDIR)/build && ../configure --disable-desktopfiles --disable-shared --enable-static --host=$(HOST) --disable-xmltools --disable-desktopfiles
+	cd $(DJVUDIR)/build && ../configure --disable-desktopfiles --disable-shared --enable-static --host=$(HOST) --disable-xmltools --disable-largefiles
 endif
 	make -C $(DJVUDIR)/build