R1:14f070a0af79

Skip anon functions in symbol generation script

Summary:
Filters closures out of symbol generator script, per @epriestley's
comment in T4334

Test Plan:
Before:
eric@eric-dev ~/phabricator/scripts/symbols: echo 'closure.php' | ./generate_php_symbols.php
function php /closure.php
d function php 10 /closure.php
function php /closure.php
a class php 3 /closure.php
a b method php 4 /closure.php

After:
eric@eric-dev ~/phabricator/scripts/symbols: echo 'closure.php' | .