Don't put configure files in /tmp

Based on patch by Vasiliy Kulikov <segoon@openwall.com>
Don't use /tmp since it is dangerous, instead put temporary files
from configure script in build directory. This is what autoconf
generated configure does.
diff --git a/.gitignore b/.gitignore
index c784159..3ba2632 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 static-syms.h
+config.*
 Config
 *.o
 *.a