PUBLISHED_FROM=44bcbb87c326a4e05e96dc0b094fd9dd1a9d4276

 - LWIP UDP sockets are always writable and they are not reported as
   such by select() (bug? featuyre?). TCP sockets are ok.
 - Always deliver MG_EV_POLL, whether we have other fd_events or not.
   Otherwise MG_EV_POLL would not be delivered at all to perma-writable
   UDP sockets (as they are on LWIP).
 - Ignore EAGAIN/EWOULDBLOCK errors while connecting, this happens
   during SSL handshake.

PUBLISHED_FROM=3b1ee0d2b0c672512da5c9d6141aba1112983426

Until issues with hardware I2C are resolved

PUBLISHED_FROM=78bced9f18b5bfbf547de06f813bf98c82eea6ea

PUBLISHED_FROM=de4b9f3e9eeafa75bb8919abacd86fb23fdefc1b

PUBLISHED_FROM=3a22eb96ff011ef8327cd1b78b56a3af86ba2c84

PUBLISHED_FROM=20c87885c8f778139d3df20507d6870070bcc787

PUBLISHED_FROM=7c81ec28457cda3a503e4ab01fc8593e474df4b8

PUBLISHED_FROM=42997efb3ddc462c33d2cf7e8ef0e922797d9901

Factor out common part of SPIFFS libc interface support from the CC3200
port and reuse it for ESP32. Minor cleanups.

PUBLISHED_FROM=19ad4049372f83046abd8eba29cfc7c2cc405671

PUBLISHED_FROM=41f43cb0e707259740de3346308f746c2a3778fd

This PR does not include `fw/platforms/pic32` since it's too dirty.

PUBLISHED_FROM=db50ba389202da80355aafe5f2c1ceeca7bffe41

Fix errors so it builds.

PUBLISHED_FROM=db9fc9ef997d6b1847117e8db9aefdc7e540f4cc

PUBLISHED_FROM=00ca7b2adabde94a683ac4d33be1f2bdbb17772f

Namely, define it if only `MG_ENABLE_HTTP_STREAMING_MULTIPART` and
`MG_ENABLE_FILESYSTEM` are on

PUBLISHED_FROM=3094738a4b76ceb09a3c2374e8d9d914b71c3441

PUBLISHED_FROM=2f6fb7ea5abdcd4ca9b06956172938ee3bc28459

And use it for `FW_ARCHITECTURE`. This is needed because with
Microchip's xc32, `-DFOO=\"bar\"` results in `FOO` being `bar`, not
`"bar"`, so we have to stringify differently.

PUBLISHED_FROM=d0aeebb55ef9e0e92a7f750104cd6600e0d9c636

PUBLISHED_FROM=bd87b901b7c1c1a4f9b0f875f0b024b672121d4a

PUBLISHED_FROM=6abc158f198f5bd032e5ab06cc0ba3373434cdbe

PUBLISHED_FROM=4d86de7f73ef9d4c0f236e1fe1201e5de792f19f

PUBLISHED_FROM=fb856714ead67390dfd7ce9d208ae5ae19ce7c6d

On PIC32MZ, this is required to get `ntohl` and friends.

PUBLISHED_FROM=82ab532cd3757df6f79215f3eaca90cd87f6c965

PUBLISHED_FROM=3c5859f06ab838bba7c95c4878c4e7e883329810

PUBLISHED_FROM=5b63325ade34b9032476fc88ac407816990f1cfc

PUBLISHED_FROM=ca0ae588290f133ef7640ca538847a63c0cb544b

PUBLISHED_FROM=e6fb19c5256b6d43359f21b325e16b415152f26f

PUBLISHED_FROM=764ea806a5d31bd545a5d99de80e2ee0234ebcab

PUBLISHED_FROM=26becdaf7dd61481b88b166ea87d44a7bc796660

Assume handshake request was declined if either MG_F_CLOSE_IMMEDIATELY _or_ MG_F_SEND_AND_CLOSE is set.

PUBLISHED_FROM=60af32a3f8890e826205465b9add2f58b1d46e5f

Free keys and cert before conf, not after

PUBLISHED_FROM=5628f56eb6973a779179d641fb425d0f14db39cf

Renegotiation is disabled, so we don't need them.
Reduces per-connection usage when idle by 3K.

PUBLISHED_FROM=24b2ac9557107f7da412dae6a42257c9b7c812d5

PUBLISHED_FROM=54774944d5402a5d6a351b4609428940c0ad20ea

 - Only allow one TCP segment in flight. Each segment is 1.5K and it
   adds up. This may increase latency, but memory is precious on ESP.
   At teh same time, optimize use of tcp_output: do not send a new segment
   on every write, only call tcp_output at the end of connection
   processing during poll.

 - Build LWIP with DNS disabled. We have our won resolver, and LWIP's
   allocates large static buffers (1K).

 - mbedTLS: Deallocate peer's certificate at the end of SSL handshake,
   reduces idle SSL connection footprint by ~1.5K.

 Some tweaks to the heap log viewer (which made all the above possible).

PUBLISHED_FROM=6e84bba64eacb2d737561e09313918104921ea80

Also performs trnasparent SPIFFS -> SLFS cert copy.

If the file's extension is .pem, convert it to DER format and put on SLFS.

PUBLISHED_FROM=364caab21969ca28a05802c4dde93a11d1e0feda

Also fixed a memory leak on reconnect: previously, each reconnect was
creating a `struct mg_connection` which was never reclaimed

PUBLISHED_FROM=eefdcf557e032ac81d5ed3aba55ac912e400148e

PUBLISHED_FROM=8e37c51c6b0bf7d0782f3a997360827471b95d2e

PUBLISHED_FROM=b17ef5bc8ec801fca91c89af5f97767a55911952

PUBLISHED_FROM=e1bb89268dfc4d51880b89b07fb2f69cb49e053b

Useful for debugging at level 3

PUBLISHED_FROM=b6a4565df0de0dccf37c182c71d2f4c852f2291a

PUBLISHED_FROM=ac54bcbc81a9ee688e8b90e261172be76a9fbacd