Remove unnecessary overhead in execunix.c related to

the timeout implementation.  Also removed unused variables
as diagnosed by the Sgi (mipspro) compiler.

Fixed const-correctness error in operations.hpp that
Sgi complained about.

There's no strerror_r function on Irix 6.5 so I replaced
it with a strerror call.

With these changes, I can now build process jam log and
start running Sgi tests.



[SVN r39378]

src/error_code.cpp

@@ -257,7 +257,14 @@ namespace
       {
         // strerror_r returns 0 on success, otherwise ERANGE if buffer too small,
         // invalid_argument if ev not a valid error number
-        if ( (result = strerror_r( ev, bp, sz )) == 0 )
+  #  if defined (__sgi)
+        const char * c_str = strerror( ev );
+        result = 0;
+        return std::string( c_str ? c_str : "invalid_argument" );
+  #  else
+        result = strerror_r( ev, bp, sz );
+  #  endif
+        if (result == 0 )
           break;
         else
         {