added faq.html

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@1159 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

doc/Makefile

-all: ffmpeg-doc.html
+all: ffmpeg-doc.html faq.html
 
 %.html: %.texi
 	texi2html -monolithic -number $<