GNU libmicrohttpd 0.9.76 hotfix

This is a hotfix release.

This only change since previous release is fixed potential DoS vector in MHD_PostProcessor discovered by Gynvael Coldwind and Dejan Alvadzijevic (CVE-2023-27371).
While the researchers have not been able to exploit this attack vector when libmicrohttpd is compiled with the standard GNU C library, it is recommended that you update MHD as soon as possible if your applications are using (optional) MHD_PostProcessor functionality.