[Ada] Fix alignment of mutex_t and cond_t type on 32-bit SPARC/Solaris

[Pierre-Marie de Rodat]

The alignment of the couple of types from System.OS_Interface was wrongly
set to 4 (32-bit) instead of 8 (64-bit) in 32-bit mode.

Tested on x86_64-pc-linux-gnu, committed on trunk

2018-07-31  Eric Botcazou  <ebotca...@adacore.com>

gcc/ada/

        *  libgnarl/s-osinte__solaris.ads (upad64_t): New private type.
        (mutex_t): Use it for 'lock' and 'data' components.
        (cond_t): Likewise for 'data' and use single 'flags' component.
--- gcc/ada/libgnarl/s-osinte__solaris.ads
+++ gcc/ada/libgnarl/s-osinte__solaris.ads
@@ -536,17 +536,18 @@ private
    end record;
    pragma Convention (C, record_type_3);
 
+   type upad64_t is new Interfaces.Unsigned_64;
+
    type mutex_t is record
       flags : record_type_3;
-      lock  : String (1 .. 8);
-      data  : String (1 .. 8);
+      lock  : upad64_t;
+      data  : upad64_t;
    end record;
    pragma Convention (C, mutex_t);
 
    type cond_t is record
-      flag  : array_type_9;
-      Xtype : unsigned_long;
-      data  : String (1 .. 8);
+      flags : record_type_3;
+      data  : upad64_t;
    end record;
    pragma Convention (C, cond_t);