build: fix examples compilation when EXESUF is not empty

Due to a wrong substitution doc/examples is not added as a prerequisite
for the objects of the example programs. This results in compiler error
due to the non-existing output directory.

Bug-Id: 636
Signed-off-by: Janne Grunau <janne-libav@jannau.net>

doc/Makefile

@@ -54,7 +54,7 @@ doc/%.1: doc/%.pod $(GENTEXI)
 	$(M)pod2man --section=1 --center=" " --release=" " $< > $@
 
 $(DOCS) doc/doxy/html: | doc/
-$(DOC_EXAMPLES:%=%.o): | doc/examples
+$(DOC_EXAMPLES:%$(EXESUF)=%.o): | doc/examples
 OBJDIRS += doc/examples
 
 DOXY_TEMPLATES  = doxy_stylesheet.css footer.html header.html