Add MANIFEST.in file.

Please add a MANIFEST.in file to ease the build of packages with python setup.py.

PATH : stratum-mining/externals/litecoin_scrypt

diff --git a/MANIFEST.in b/MANIFEST.in
new file mode 100644
index 0000000..3ebbeef
--- /dev/null
+++ b/MANIFEST.in
@@ -0,0 +1 @@
+include scrypt.h
