It now accounts for the number of rx pool buffers used and the
available memory when deciding the number of ooseq buffers to retain.
Enable the TCP Selective ACK support which appears to help a lot on
lossy wifi when using the OOSEQ option.
Also reduces the IRAM footprint of the fatal exception handler, as only
the prelude (which disables interrupts & enables the flash mapping) is
in IRAM now.
Closes#54, relevant to #133.
* This fixes the problem of axTLS symbols hmac_md5/hmac_sha1 having same
name as symbols in libwpa (which have incompatible signatures)
* Also allows for easier identification and piece-by-piece removal of
binary functions.
* Some libc symbols are not renamed, list is in lib/symbols_norename.txt
