build [flock] if "with-bird=yes"

we don't disable it by default, in order to keep confusion low.
practically no one still has the device, and the help-patch is rather
low-leverl.

Makefile

@@ -2,6 +2,8 @@
 
 lib.name = comport
 
+with-bird=no
+
 class.sources = comport.c
 
 datafiles = \
@@ -13,6 +15,13 @@ datafiles = \
 	README.txt \
 	$(empty)
 
+
+ifeq ($(with-bird),yes)
+ class.sources += bird/bird.c
+ datafiles += bird/bird-help.pd
+endif
+
+
 # This Makefile is based on the Makefile from pd-lib-builder written by
 # Katja Vetter. You can get it from:
 # https://github.com/pure-data/pd-lib-builder