For both OpenSSL and mbedTLS

PUBLISHED_FROM=0bfd5f128b4c4c062cb6f0ca0da9b30790aa8bf8

PUBLISHED_FROM=f0fe58c9f01ef0c7b491ed0e5f51b983e4119507

PUBLISHED_FROM=7864ffa26cb553f5d4a93248f67c288327ec23b0

Optional specification of SSL/TLS cipher suites.

PUBLISHED_FROM=e8968c6c7a92f10514d3ee575c2fb9be862e6cf8

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=cccd28ef43ec4e08fa52340ce78bda10db5ac27a

PUBLISHED_FROM=182c43c3bd82190cb816c8ebaddccc13a94950d0

PUBLISHED_FROM=0454cdeec5c7120eb4bf905fdd5b7abdcb4003c2

PUBLISHED_FROM=196199fd02ec9b20d1e76d1414bfafa624f9ebce

Currently only OpenSSL API impl, but the plan is to add more.

PUBLISHED_FROM=c85b26fa2312047768bdcf3eca583e60862aba90

PUBLISHED_FROM=f554cc63dfea12455fe5e428c6ce5f3152774f8e

PUBLISHED_FROM=39a1c2a271c5cd961670e11c830105c17ba0b2e4

PUBLISHED_FROM=f03b963aaec02574e47c28ee8033551440b94f2d

PUBLISHED_FROM=2b82f3793b3c6d0cf1266e4cc0e67930f43002c5

PUBLISHED_FROM=46496c2d5340a0bbe4fe1c6c9ff187bc65d2d35f

PUBLISHED_FROM=cded8f36e2833e7c256ba6cbca0ebf1f6012dee7

PUBLISHED_FROM=3caea25dec11260561349fa096547bd62ecdb509

PUBLISHED_FROM=6455082726781aab819a7f8645e81adaa7fc7669

This event is sent at the end of the request

PUBLISHED_FROM=0b841a26320e3edbf73126e2ed8d286d4e5f3fa8

PUBLISHED_FROM=017e707ea2bd7b1d1972fbb92e5d98c74e17e9d0

PUBLISHED_FROM=00772400bce7c15368d91741092ebc8ab0842e19

PUBLISHED_FROM=51652f0157bb951a43508f0fe948c62c351e96ba

PUBLISHED_FROM=623dda0737c8426754044880713c1283c4b181b6

PUBLISHED_FROM=73ef8ae768585d3c204e6e022848f49e8f4a8de2

Disable sync resolver by default.

PUBLISHED_FROM=dbaed194e5fe211c07564fe6880649a1aee7f662

Possible values:
  MG_NET_IF_SOCKET (1) - traditional BSD socket API
  MG_NET_IF_SIMPLELINK (2) - TI's SimpleLink socket interface
  MG_NET_IF_LWIP_LOW_LEVEL - a net_if implementation that uses LWIP's
    low-level API, when LWIP_SOCKET is not available.

PUBLISHED_FROM=a5c0aebb7b6bdb1f1f4cb3210763d16f3ab5e133

PUBLISHED_FROM=81b6289a4b54043df557142f0de8cc66bc5190d4

PUBLISHED_FROM=9fd0cebfa8df53b5d9574a8d013305ddda5e7a18

"#if FOO" still works with simple -DFOO, but gives more flexibility.
Specifically, if user expressed no preference (FOO is not defined),
we can apply reasonable defaults (this is the legitimate use of ifdef).

In short, from now on, please use

 #if MG_ENABLE_FOO

instead of

 #ifdef MG_ENABLE_FOO

Since we are all used to #ifdef, this change also adds a precommit check
to police this. Specifically, in *.h and *.c files that are Copyright Cesanta,
"ifdef" and "if defined()" are not allowed to be used with macros that contain
ENABLE or DISABLE, unless the like also contains "ifdef-ok".

Hence, if you are sure you want to use ifdef, use this:

 #ifdef MG_ENABLE_FOO /* ifdef-ok */

PUBLISHED_FROM=9be829448f53cff575d6cae8b9945fb12531c15a

This is the variant of MG_EV_SSI_CALL with context of the SSI call being
processed in addition to the tag argument. Specifically, call handler
now gets access to the HTTP request and the name of the file being processed.

MG_EV_SSI_CALL is preserved for backward compatibility.

PUBLISHED_FROM=eeea7487c062505abdb23b6f64994ff7a6b60ff8

PUBLISHED_FROM=77cd3df9959b0e3a2550d1581586e69878bbee0d

PUBLISHED_FROM=f45e06aeba1c00212078d539b6f74cb8bd054326

Main TODOs:
1. the spec requires the impl to resend the reply once and
   to send gratuitous updates

2. advertise our clubby services as DNS-SD sub-services.

---

Tested with:

1. https://play.google.com/store/apps/details?id=com.grokkt.android.bonjour&hl=en
2. https://play.google.com/store/apps/details?id=com.druk.bonjour.browser&hl=en
3. osx `dns-sd`

Works well enough; it doesn't have some glitches due the fact that we
don't retransmit yet and we don't send gratuitous updates.

PUBLISHED_FROM=38d7a50beb274d4aeeda5b0b58e44dfa0789da84

PUBLISHED_FROM=da57dfe52e315dc1901d761289f0445be6e93cea

PUBLISHED_FROM=da5f7f80a9876ac4f1889a1176a3048f47980659

PUBLISHED_FROM=da57dfe52e315dc1901d761289f0445be6e93cea

PUBLISHED_FROM=dbf75bfba087f1b0aa0531e5003ba3e69ed1a6ab

PUBLISHED_FROM=293a54ab09e6879b6f0c36975a137eeaeff92098

On my way, fixed a couple of cases where we had `()` in the header, and
non-empty argument list in the source file.

PUBLISHED_FROM=5519526cf84e2bbd425a726fcc112fea1a95cbf1

PUBLISHED_FROM=e9a4e5c7b4a1d03b93a2a79e29de19e60e919929