Fix code that causes HHVM warnings and notices when viewing the docs. These fixes should remove all the doc based warnings we have been getting.

Test Plan:
All these errors go away. Error log file becomes more manageable.

HipHop Warning: File not found: /data/users/joelm/hack-hhvm-docs/includ
e/../manual/en/toc/langref.inc in /data/users/joelm/hack-hhvm-docs/incl
ude/layout.inc on line 652
HipHop Notice: Undefined variable: TOC in /data/users/joelm/hack-hhvm-d
ocs/include/layout.inc on line 657
HipHop Notice: Undefined variable: title in /data/users/joelm/hack-hhvm
-docs/include/layout.inc on line 667

Reviewers: jpearce, sgolemon

Reviewed By: jpearce

Differential Revision: https://phabricator.fb.com/D1244514