core.sys.posix.signal: Fix size of sigevent and siginfo_t on 64bit.

Because the static if condition determining __SI_PAD_SIZE and
__SIGEV_PAD_SIZE being default false, the overall size of sigevent and
siginfo_t was 8 bytes too much, this affects all users of these types
also, such as core.sys.posix.aio.

Author: ibuclaw

src/core/sys/posix/signal.d

@@ -941,7 +941,7 @@ version( CRuntime_Glibc )
 
     private enum __SI_MAX_SIZE = 128;
 
-    static if( false /* __WORDSIZE == 64 */ )
+    static if( __WORDSIZE == 64 )
     {
         private enum __SI_PAD_SIZE = ((__SI_MAX_SIZE / int.sizeof) - 4);
     }
@@ -1740,7 +1740,7 @@ else version( CRuntime_UClibc )
 
     private enum __SI_MAX_SIZE = 128;
 
-    static if( false /* __WORDSIZE == 64 */ )
+    static if( __WORDSIZE == 64 )
     {
         private enum __SI_PAD_SIZE = ((__SI_MAX_SIZE / int.sizeof) - 4);
     }
@@ -3450,7 +3450,7 @@ version( CRuntime_Glibc )
 {
     private enum __SIGEV_MAX_SIZE = 64;
 
-    static if( false /* __WORDSIZE == 64 */ )
+    static if( __WORDSIZE == 64 )
     {
         private enum __SIGEV_PAD_SIZE = ((__SIGEV_MAX_SIZE / int.sizeof) - 4);
     }
@@ -3611,7 +3611,7 @@ else version( CRuntime_UClibc )
 {
     private enum __SIGEV_MAX_SIZE = 64;
 
-    static if( false /* __WORDSIZE == 64 */ )
+    static if( __WORDSIZE == 64 )
     {
         private enum __SIGEV_PAD_SIZE = ((__SIGEV_MAX_SIZE / int.sizeof) - 4);
     }