move tbl/htc.h to installed headers

consequence of 90c4b747:
if cache_varnishd.h is installed, we also need table files
used therein.

include/Makefile.am

@@ -16,6 +16,7 @@ nobase_pkginclude_HEADERS = \
 	tbl/h2_frames.h \
 	tbl/h2_settings.h \
 	tbl/h2_stream.h \
+	tbl/htc.h \
 	tbl/http_headers.h \
 	tbl/http_response.h \
 	tbl/locks.h \
@@ -98,8 +99,7 @@ nobase_noinst_HEADERS = \
 	vss.h \
 	vtcp.h \
 	vtree.h \
-	vus.h \
-	tbl/htc.h
+	vus.h
 
 ## keep in sync with lib/libvcc/Makefile.am
 vcl.h: \