Configure: typo fixed.

auto/lib/google-perftools/conf

diff --git a/auto/lib/google-perftools/conf b/auto/lib/google-perftools/conf
index 7a9de30..5d5ddae 100644
--- a/auto/lib/google-perftools/conf
+++ b/auto/lib/google-perftools/conf
@@ -52,7 +52,7 @@
 
 cat << END
 
-$0: error: the Google perftool module requires the Google perftools
+$0: error: the Google perftools module requires the Google perftools
 library. You can either do not enable the module or install the library.
 
 END