Allow a php shebang

Mark as safe a file which only outputs a php shebang (using /usr/bin/env)

Change-Id: Iff449ef61ad16d41f19141f3f2cd1f4cea777c08
Allow whitelisting additional functions on the command line.

The functions to allow as safe for a web application are passed
as a comma-separated list to the new parameter ‘--allow’,
ie. --allow=function1,function2,function3

Change-Id: I172e78b6cda60689b890a1192d85d56fac65f8e2