Bump header size from 2048 to 8192

[danhunsaker]

• Update setup.h to change the size
• Update main.c to check the size rather than use a hard coded value
• Update init.c to check the size and offer half to the config; this allows command line arguments and internals to have space to add any additional needed headers to the request

Hopefully these updated values will be enough to handle users' needs well into the future.

[danhunsaker]

This should address at least #218