[Ada] Refine documentation of Monotonic_Clock to reflect reality

2018-05-29  Doug Rupp  <rupp@adacore.com>

gcc/ada/

	* libgnarl/s-taprop.ads (Monotonic_Clock): Refine documentation to
	reflect reality.

From-SVN: r260863

gcc/ada/ChangeLog

+2018-05-29  Doug Rupp  <rupp@adacore.com>
+
+	* libgnarl/s-taprop.ads (Monotonic_Clock): Refine documentation to
+	reflect reality.
+
 2018-05-29  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
 	* exp_ch4.adb (Expand_N_Op_Abs): Always do range check against 'First.

gcc/ada/libgnarl/s-taprop.ads

@@ -340,9 +340,9 @@ package System.Task_Primitives.Operations is
 
    function Monotonic_Clock return Duration;
    pragma Inline (Monotonic_Clock);
-   --  Returns "absolute" time, represented as an offset relative to "the
-   --  Epoch", which is Jan 1, 1970. This clock implementation is immune to
-   --  the system's clock changes.
+   --  Returns "absolute" time, represented as an offset relative to an
+   --  unspecified Epoch. This clock implementation is immune to the
+   --  system's clock changes.
 
    function RT_Resolution return Duration;
    pragma Inline (RT_Resolution);