patch 8.1.0106: build fails when HAVE_DATE_TIME is undefined

Problem:    Build fails when HAVE_DATE_TIME is undefined.
Solution:   Always define init_longVersion(). (Christian Brabandt,
            closes #3075)
diff --git a/src/version.c b/src/version.c
index 85b6797..1969072 100644
--- a/src/version.c
+++ b/src/version.c
@@ -71,6 +71,12 @@
 # endif
 #else
 char	*longVersion = VIM_VERSION_LONG;
+
+    void
+init_longVersion(void)
+{
+    // nothing to do
+}
 #endif
 
 static void list_features(void);
@@ -784,6 +790,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    106,
+/**/
     105,
 /**/
     104,