libmicrohttpd: update to version 0.9.77

Changelog:

This is mostly a bugfix release.
This version created by taking patches from the current development branch and
back-porting them on top of version 0.9.76.
The most notable changes are: some improvements for Digest and Basic
authorizations, fixed efficiency for TLS upgraded connections, fixed
processing of folded headers in requests, fixed functionality with blocking
sockets, improved and fixed internal test-suite.

The more detailed list of the important changes:

API changes:
+ Added new function MHD_get_version_bin().

Improvements and enhancements:
* Digest Auth: changed algorithm identifiers in server generated headers from
"md5" / "sha-256" to "MD5" / "SHA-256" to better match RFC (while clients
should use caseless matching).
* Improved Base64 decoding by new implementation with robust input data
validation checks.
* Improved configure for cross-compiling, for better compatibility with POSIX
and for better compatibility with the latest compiler versions.
* New internal tests: for Base64 decoding, Basic Auth and folded headers.
* Supported new libcurl API in tests to mute deprecation warnings.
* Supported ARM and ARM64 for VC compilers.

Functionality changes:
* any negative number returned by response data generation callback function
is treated as an error. Previously negative values except predefined error
codes could produce undefined behaviour.
* Added handling of "DEBUG" preprocessor macro as an alias of "_DEBUG".

Fixes:
# Fixed functionality with blocking sockets.
# Fixed very inefficient data pumping for upgraded TLS connections.
# Fixed processing of folded headers in the requests.
# Fixed data races when closing upgraded connection.
# Removed duplication of "Connection: upgrade" header.
# Digest auth: fixed thread sync to avoid "stale hash" results.
# Fixed harmless unwanted extra data processing resulting in triggering of the
assert.
# Fixed tests for LTO.
# Removed removed non-portable functions in examples.
# Fixed delayed call of connection notification callback in
thread-per-connection mode.
# Fixed Address Sanitizer unpoison of memory when memory pool is destroyed.
This fixed periodic ASAN error when used for a long time with the sanitizer.
# Fixed compiler warnings in library code, examples, tests and configure
checks.
# New TLS certificates for test-suite: all with SAN fields and SHA-256 hash.
# Tests: fixed tests on Darwin 22.x (Ventura).
# Tests: redesigned one tests group to avoid stress-testing of the OS.


(nikita)