[vala] build: Use --use-header for libvaladoc

[Rico Tzschichholz <ricotz src gnome org>]

commit 3b47d33ab8689b70074eced217291a9582ced739
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Jul 3 10:34:42 2017 +0200

    build: Use --use-header for libvaladoc
    
    Reduces the size of generated c-sources while avoiding redefinitions.

 libvaladoc/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/libvaladoc/Makefile.am b/libvaladoc/Makefile.am
index 4ce7949..387eeb8 100644
--- a/libvaladoc/Makefile.am
+++ b/libvaladoc/Makefile.am
@@ -177,6 +177,7 @@ libvaladoc.vala.stamp: $(libvaladoc_la_VALASOURCES)
                --basedir $(srcdir) \
                --directory $(builddir) \
                -C \
+               --use-header \
                -H valadoc.h \
                --library valadoc \
                --vapi valadoc@PACKAGE_SUFFIX@.vapi \