BUG/MEDIUM: cache: Don't cache objects if the size of headers is too big

HTTP responses with headers than impinge upon the reserve must not be
cached. Otherwise, there is no warranty to have enough space to add the header
"Age" when such cached responses are delivered.

This patch must be backported to 2.0 and 1.9. For these versions, the same must
be done for the legacy HTTP mode.
1 file changed