Inspect POST buffer in mg_get_var() only if first call of get_var() returns -1

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In mg_get_var() the first call of get_var() inspects the variables of
the query string. If the requested variable is found but the destination
buffer is too small to hold the variable, return -2 right away. If it's
not found, make the second call of get_var() to inspect the POST buffer.

Reverting (socket < 0) checks to avoid Windows build failure.

Adding a check to avoid undefined behavior if socket is out of the bound...

safety belt : scan_directory() can return without setting arr to a valid value

OS2 and Android NDK fixes

Note that in Android NDK st_mtime is long unsigned int

Correctly handle _CRT_SECURE_NO_WARNINGS already being set in project se...

Fixed Memory Leak

Added PATCH to list of valid HTTP Methods.

Fix remove_double_dots_and_double_slashes removing all the dots leading http server to serve wrong URI

If the uri is something like '/js/...jquery.js', remove_double_dots_and_double_slashes will remove the 3 dots and the http server will serves the /js/jquery.js file.
remove_double_dots_and_double_slashes should check if a dot or double dots is followed by a slash (or backslash) and only remove this to avoid disclosure attack.