Removed /Gd from windows compilation flags, cause that breaks sqlite3 + fts (qsort callback is __cdecl, not __stdcall)

Detect Window's style slashes in mg_upload file names

MKCOL and DELETE

support serving pre-gzipped files

Added bounds checking for listening_ports.

support serving pre-gzipped files transparently provided the user agent accepts gzip content-encoding. The feature breaks if the user agent makes a range request within a gzipped file, and returns 501 in this case