build: Disable avconv more completely while leaving the user the option to enable it

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Makefile

@@ -47,7 +47,7 @@ include $(SRC_PATH)/common.mak
 FF_EXTRALIBS := $(FFEXTRALIBS)
 FF_DEP_LIBS  := $(DEP_LIBS)
 
-all: $(filter-out avconv, $(PROGS))
+all: $(PROGS)
 
 $(PROGS): %$(EXESUF): %$(PROGSSUF)_g$(EXESUF)
 	$(CP) $< $@$(PROGSSUF)

configure

@@ -81,7 +81,7 @@ Configuration options:
                            and binaries will be unredistributable [no]
   --disable-doc            do not build documentation
   --disable-ffmpeg         disable ffmpeg build
-  --disable-avconv         disable avconv build
+  --enable-avconv          enable  avconv build
   --disable-ffplay         disable ffplay build
   --disable-ffprobe        disable ffprobe build
   --disable-ffserver       disable ffserver build
@@ -1799,7 +1799,6 @@ enable debug
 enable doc
 enable fastdiv
 enable ffmpeg
-enable avconv
 enable ffplay
 enable ffprobe
 enable ffserver