Post-merge fix of the fixes for NPTL configuration (bug#2173, bug#5871, and bug#9497).

config/ac-macros/openssl.m4:
  "Configure" variable 'IS_LINUX' renamed to 'TARGET_LINUX'.
  Manual merge: In 4.1, this was in 'acinclude.m4'.
include/my_global.h:
  As we have a new CPP symbol, this should be "undef"ed explicitly.

config/ac-macros/openssl.m4

@@ -44,7 +44,7 @@ AC_DEFUN([MYSQL_FIND_OPENSSL], [
  if test -z "$OPENSSL_LIB" -o -z "$OPENSSL_INCLUDE" ; then
    echo "Could not find an installation of OpenSSL"
    if test -n "$OPENSSL_LIB" ; then
-    if test "$IS_LINUX" = "true"; then
+    if test "$TARGET_LINUX" = "true"; then
       echo "Looks like you've forgotten to install OpenSSL development RPM"
     fi
    fi

include/my_global.h

@@ -107,6 +107,7 @@
 #undef THREAD
 #undef HAVE_mit_thread
 #undef HAVE_LINUXTHREADS
+#undef HAVE_NPTL
 #undef HAVE_UNIXWARE7_THREADS
 #endif