R1:b71e1c15ef93

Detect which PHP SAPI the CLI binary uses during setup

Summary:
- PHP uses a SAPI ("server API") to determine how it interacts with the caller
(e.g., how to read the environment, how to read flags, what code to execute).
- There are several different SAPIs: cli, cgi, cgi-fcgi, apache, etc.
- Each SAPI has different behavior -- for instance, the "cgi" SAPI emits some
CGI headers unless told not to, so a script like 'echo "x"' actually echoes some
headers and then 'x' as an HTTP body.
- In some…