Introduce and use gnc_time64_get_day_neutral

This function complements gnc_time64_get_day_begin/end. There was
time64CanonicalDayTime but this returned noon of the given day, where we
want 10:59am in most cases. I haven't changed time64CanonicalDayTime
directly as that may break assumptions in other parts of the code.
Instead I have created a new function that can be gradually introduced.

libgnucash/engine/gnc-date.cpp

@@ -1243,6 +1243,15 @@ gnc_tm_get_day_start (struct tm *tm, time64 time_val)
     gnc_tm_set_day_start(tm);
 }
 
+static void
+gnc_tm_get_day_neutral (struct tm *tm, time64 time_val)
+{
+    /* Get the equivalent time structure */
+    if (!gnc_localtime_r(&time_val, tm))
+        return;
+    gnc_tm_set_day_neutral(tm);
+}
+
 static void
 gnc_tm_get_day_end (struct tm *tm, time64 time_val)
 {
@@ -1263,6 +1272,17 @@ gnc_time64_get_day_start (time64 time_val)
     return new_time;
 }
 
+time64
+gnc_time64_get_day_neutral (time64 time_val)
+{
+    struct tm tm;
+    time64 new_time;
+
+    gnc_tm_get_day_neutral(&tm, time_val);
+    new_time = gnc_mktime(&tm);
+    return new_time;
+}
+
 time64
 gnc_time64_get_day_end (time64 time_val)
 {

libgnucash/engine/gnc-date.h

@@ -524,6 +524,20 @@ void gnc_tm_set_day_start (struct tm *tm)
     tm->tm_sec = 0;
 }
 
+/** The gnc_tm_set_day_neutral() inline routine will set the appropriate
+ *  fields in the struct tm to indicate 10:59am of that day.  This
+ *  routine assumes that the contents of the data structure is already
+ *  in normalized form.*/
+static inline
+void gnc_tm_set_day_neutral (struct tm *tm)
+{
+    /* First second of the day */
+    g_return_if_fail (tm != NULL);
+    tm->tm_hour = 10;
+    tm->tm_min = 59;
+    tm->tm_sec = 0;
+}
+
 /** The gnc_tm_set_day_middle() inline routine will set the appropriate
  *  fields in the struct tm to indicate noon of that day.  This
  *  routine assumes that the contents of the data structure is already
@@ -553,9 +567,13 @@ void gnc_tm_set_day_end (struct tm *tm)
 }
 
 /** The gnc_time64_get_day_start() routine will take the given time in
- *  seconds and adjust it to the last second of that day. */
+ *  seconds and adjust it to the first second of that day. */
 time64 gnc_time64_get_day_start(time64 time_val);
 
+/** The gnc_time64_get_day_netural() routine will take the given time in
+ *  seconds and adjust it to 10:59am of that day. */
+time64 gnc_time64_get_day_neutral(time64 time_val);
+
 /** The gnc_time64_get_day_end() routine will take the given time in
  *  seconds and adjust it to the last second of that day. */
 time64 gnc_time64_get_day_end(time64 time_val);