Add stubs for various standard functions

[kocsismate]

(I promise this is my last similar PR for a while. :D)

Stubs for functions defined in the following files:

• info.c
• iptc.c
• levenshtein.c
• link.c
• mail.c
• math.c
• microtime.c
• pack.c
• password.c
• proc_open.c
• quot_print.c
• mt_rand.c
• random.c

[carusogabriel]

@kocsismate Please check the Zend/tests/bug75290.phpt test file, it's now failing.

[kocsismate]

@carusogabriel Thanks for the heads up! I managed to fix the test locally by reverting the parameter name changes of some maths functions.