Deprecate date options with a time of day setting.

Removing the only use, an example in hello-world.scm. GnuCash doesn't
use this value in any of its own report options and the feature will
be removed in GnuCash 5.

Related to bug 798297 Pref "Use 24-hour clock" obsolete?.

gnucash/report/reports/example/hello-world.scm

@@ -94,15 +94,6 @@
       (lambda () (cons 'absolute (current-time)))
       #f 'absolute #f ))
     
-    ;; This is another date option, but the user can also select
-    ;; the time.
-    (add-option
-     (gnc:make-date-option
-      (N_ "Hello, World!") (N_ "Time and Date Option")
-      "e" (N_ "This is a date option with time.")
-      (lambda () (cons 'absolute (current-time)))
-      #t 'absolute #f ))
-    
     (add-option
      (gnc:make-date-option
       (N_ "Hello, World!") (N_ "Combo Date Option")
@@ -234,8 +225,6 @@ option like this.")
         (string-val   (op-value "Hello, World!" "String Option"))
         (date-val     (gnc:date-option-absolute-time
                        (op-value "Hello, World!" "Just a Date Option")))
-        (date2-val    (gnc:date-option-absolute-time
-                       (op-value "Hello, World!" "Time and Date Option")))
         (rel-date-val (gnc:date-option-absolute-time
                        (op-value "Hello, World!" "Relative Date Option")))
         (combo-date-val (gnc:date-option-absolute-time
@@ -258,7 +247,6 @@ option like this.")
     ;; qof-print-date
     (let ((time-string (gnc-print-time64 (current-time) "%X"))
           (date-string (gnc-print-time64 date-val "%x"))
-          (date-string2 (gnc-print-time64 date2-val "%x %X"))
           (rel-date-string (gnc-print-time64 rel-date-val "%x"))
           (combo-date-string (gnc-print-time64 combo-date-val "%x")))
 
@@ -369,11 +357,6 @@ new, totally cool report, consult the mailing list ~a.")
           (G_ "The date option is ~a.") 
           (gnc:html-markup-b date-string)))
 
-        (gnc:html-markup-p
-         (gnc:html-markup/format
-          (G_ "The date and time option is ~a.") 
-          (gnc:html-markup-b date-string2)))
-
         (gnc:html-markup-p
          (gnc:html-markup/format 
           (G_ "The relative date option is ~a.")

libgnucash/app-utils/options.scm

@@ -719,10 +719,14 @@ the option '~a'."))
         (begin
           (rpterror-earlier "date" item (car full-list))
           0)))
-  (let* ((value (default-getter))
+  (if show-time
+      (issue-deprecation-warning
+       (format #f "Date options with time of day values are deprecated and will be removed in GnuCash 5.")))
+
+ (let* ((value (default-getter))
          (value->string (lambda ()
                           (string-append "'" (gnc:value->string value)))))
-    (gnc:make-option
+     (gnc:make-option
      section name sort-tag 'date documentation-string
      (lambda () value)
      (lambda (date)