properly declare vtc_h2_dectbl.h to automake and git

in order to have it build first and cleaned up

fixes this issue when switching to an older branch:

$ git checkout ...
error: The following untracked working tree files would be overwritten
by checkout:
	bin/varnishtest/vtc_h2_dectbl.h
Please move or remove them before you switch branches.
Aborting

.gitignore

@@ -51,6 +51,7 @@ cscope.*out
 # Various auto-generated code snippets
 /bin/varnishd/vhp_hufdec.h
 /bin/varnishd/vhp_gen_hufdec
+/bin/varnishtest/vtc_h2_dectbl.h
 /include/vcl.h
 /include/vrt_obj.h
 /include/vmod_abi.h

bin/varnishtest/Makefile.am

@@ -91,4 +91,8 @@ vtc_h2_dectbl.h: huffman_gen.py $(top_srcdir)/include/tbl/vhp_huffman.h
 	    $(top_srcdir)/include/tbl/vhp_huffman.h > $@_
 	mv $@_ $@
 
-CLEANFILES = $(builddir)/teken_state.h
+BUILT_SOURCES = vtc_h2_dectbl.h
+
+CLEANFILES = \
+	$(builddir)/teken_state.h	\
+	$(BUILT_SOURCES)