fix typo in name of LibreSSL in HPHPFindLibs.cmake

Summary: Closes https://github.com/facebook/hhvm/pull/4466

Reviewed By: @paulbiss

Differential Revision: D1742589

Signature: t1:1742589:1418766759:958691750c0a399ff9bb7114d2702538da36f943
Build with system fastlz if it exists

Summary: Fedora ships with fastlz package. This PR allows you to build with it.
Closes https://github.com/facebook/hhvm/pull/4470

Reviewed By: @paulbiss

Differential Revision: D1742586

Signature: t1:1742586:1418766893:37c3a5a36762769c2cd88aed57853020cfebfbe5