[folks] build: Fix version check for latest versions of valadoc

[Philip Withnall <pwithnall src gnome org>]

commit af8fd6605e3360491b7ac7bbdb80169eef60f1b0
Author: Philip Withnall <withnall endlessm com>
Date:   Sun Jul 2 22:16:25 2017 +0100

    build: Fix version check for latest versions of valadoc
    
    It went and inconveniently changed its pkg-config name without actually
    breaking API.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 configure.ac |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 70670c0..0d2c49a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -583,7 +583,10 @@ AM_CONDITIONAL([ENABLE_DOCS], [test x$enable_docs = xyes])
 have_valadoc=no
 AS_IF([test x$enable_docs = xyes], [
   # make sure the library is new enough and the program exists
-  PKG_CHECK_MODULES([VALADOC], [valadoc-1.0 >= $VALADOC_REQUIRED])
+  # Valadoc changed its pkg-config name when it was merged into libvala.
+  PKG_CHECK_MODULES([VALADOC],[valadoc-0.38 >= $VALADOC_REQUIRED],,[
+    PKG_CHECK_MODULES([VALADOC],[valadoc-1.0 >= $VALADOC_REQUIRED])
+  ])
   AC_PATH_PROG([VALADOC], [valadoc], [:])
   AS_IF([test "$VALADOC" != :], have_valadoc=yes)
 ])