[Ada] Fix parentheses in comments and "library-level" punctuation

When acting as an adjective, it is "library-level something"; when
acting as a noun, it is "something at the library level".

2018-11-14  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* exp_dbug.ads, sem_util.ads: Minor fixes in comments.

From-SVN: r266109

gcc/ada/ChangeLog

+2018-11-14  Piotr Trojanek  <trojanek@adacore.com>
+
+	* exp_dbug.ads, sem_util.ads: Minor fixes in comments.
+
 2018-11-14  Arnaud Charlet  <charlet@adacore.com>
 
 	* adabkend.adb (Scan_Back_End_Switches): Handle -gx switches

gcc/ada/exp_dbug.ads

@@ -65,7 +65,7 @@ package Exp_Dbug is
 
    --  For global entities, the encoded name includes all components of the
    --  fully expanded name (but omitting Standard at the start). For example,
-   --  if a library level child package P.Q has an embedded package R, and
+   --  if a library-level child package P.Q has an embedded package R, and
    --  there is an entity in this embedded package whose name is S, the encoded
    --  name will include the components p.q.r.s.
 
@@ -291,7 +291,7 @@ package Exp_Dbug is
       --    #6.  x__y__m3          (no BNPE's in signt)
       --    #7.  x__y__j           (no BNPE's in sight)
       --    #8.  k__z              (no BNPE's, only up to procedure)
-      --    #9   _ada_x__m3        (library level subprogram)
+      --    #9   _ada_x__m3        (library-level subprogram)
 
       --  Note that we have instances here of both kind of potential name
       --  clashes, and the above examples show how the encodings avoid the
@@ -479,7 +479,7 @@ package Exp_Dbug is
    --  the changes till just before gigi is called, we avoid any concerns
    --  about such effects. Gigi itself does not use the names except for
    --  output of names for debugging purposes (which is why we are doing
-   --  the name changes in the first place.
+   --  the name changes in the first place).
 
    --  Note: the routines Get_Unqualified_[Decoded]_Name_String in Namet are
    --  useful to remove qualification from a name qualified by the call to

gcc/ada/sem_util.ads

@@ -1006,7 +1006,7 @@ package Sem_Util is
    function Get_Default_External_Name (E : Node_Or_Entity_Id) return Node_Id;
    --  This is used to construct the string literal node representing a
    --  default external name, i.e. one that is constructed from the name of an
-   --  entity, or (in the case of extended DEC import/export pragmas, an
+   --  entity, or (in the case of extended DEC import/export pragmas) an
    --  identifier provided as the external name. Letters in the name are
    --  according to the setting of Opt.External_Name_Default_Casing.