Adjust our fairly tight header limits.
Adjust our fairly tight header limits.

Chromium was running into the FIELDS_SIZE limit during file submission.

Fields Chromium was sending:
Host
Connection
Content-Length
Cache-Control
Accept
Origin
User-Agent
Content-Type
DNT
Referer
Accept-Encoding
Accept-Language
Cookie

13 fields for a total of 145 bytes (including nul delimeters). Our previous cap was 128 bytes, so I raised it to 256.

Conversely, I lowered VALUE_MAX from 1024 to 512, and VALUES_MAX (the total) from 16KB to 8KB.

btrask/stronglink,Ryezhang/stronglink,nkatsaros/stronglink,iOSCowboy/stronglink,shaunstanislaus/stronglink,Ryezhang/stronglink,nkatsaros/stronglink,btrask/stronglink,guiquanz/stronglink,feld/stronglink,iOSCowboy/stronglink,feld/stronglink,iOSCowboy/stronglink,Lacra17/stronglink,guiquanz/stronglink,btrask/stronglink,yamingd/stronglink,rmoorman/stronglink,rmoorman/stronglink,rmoorman/stronglink,yamingd/stronglink,guiquanz/stronglink,feld/stronglink,shaunstanislaus/stronglink,yamingd/stronglink,btrask/stronglink,shaunstanislaus/stronglink,Lacra17/stronglink,Ryezhang/stronglink,nkatsaros/stronglink,Lacra17/stronglink