libtasn1.h.in: update section documentation

Follow new gtk-doc section documentation format.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
diff --git a/lib/includes/libtasn1.h.in b/lib/includes/libtasn1.h.in
index 66357de..4889e7b 100644
--- a/lib/includes/libtasn1.h.in
+++ b/lib/includes/libtasn1.h.in
@@ -21,12 +21,8 @@
  */
 
 /**
- * libtasn1:Short_Description:
- *
- * GNU ASN.1 library
- */
-/**
- * libtasn1:Long_Description:
+ * SECTION:libtasn1
+ * @short_description: GNU ASN.1 library
  *
  * The Libtasn1 library provides Abstract Syntax Notation One (ASN.1, as
  * specified by the X.680 ITU-T recommendation) parsing and structures