Add "testclean" target to .PHONY

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17948 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

Makefile

@@ -303,4 +303,4 @@ tests/seek_test$(EXESUF): tests/seek_test.c $(FF_DEP_LIBS)
 	$(CC) $(FF_LDFLAGS) $(CFLAGS) -o $@ $< $(FF_EXTRALIBS)
 
 
-.PHONY: lib documentation *test regtest-* swscale-error zlib-error alltools check
+.PHONY: lib documentation *test regtest-* testclean swscale-error zlib-error alltools check