build: require clang >= 3.6

3.5 fails with "error: debug information for auto is not yet supported"

Change-Id: I77ac4a064959b26796a4bf3f1dea7c3c08ea60a3
diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index 0eaf52a..5d94e35 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -29,7 +29,7 @@
 Required:
 ~~~~~~~~~
 
--  GCC >= 5.3, or clang >= 3.5
+-  GCC >= 5.3, or clang >= 3.6
 -  ``python2`` >= 2.7, or ``python3`` >= 3.4
 -  ``libsqlite3``
 -  OpenSSL >= 1.0.2