check for PR_SET_NAME being defined

Depending on what glibc/kernel headers you are compiling against,
PR_SET_NAME may or may not be defined.  Do the right thing if
PR_SET_NAME isn't defined and skip setting the process name.

Signed-off-by: Nathan Froyd <froydnj@codesourcery.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Message-Id:

vl.c

@@ -301,7 +301,7 @@ void hw_error(const char *fmt, ...)
 
 static void set_proc_name(const char *s)
 {
-#ifdef __linux__
+#if defined(__linux__) && defined(PR_SET_NAME)
     char name[16];
     if (!s)
         return;