Add autoconf macros that might not be installed with a usual autotools setup

This is recommended practice as per
https://www.gnu.org/software/automake/manual/html_node/Local-Macros.html.

It fixes the problem that arose when one of the maintainers could not build LibVNCServer
after https://github.com/LibVNC/libvncserver/pull/38 was merged.

Symptoms included

  checking whether make sets $(MAKE)... yes
  ./configure: line 2481: syntax error near unexpected token `rfb/rfbconfig.h'
  ./configure: line 2481: `AX_PREFIX_CONFIG_H(rfb/rfbconfig.h)'

until autoconf-archive was installed (which was a previously unmentioned
requirement for Pull Request #38) – this is not always an option, in particular
when the project needs to be built using a system-wide autoconf installation
that cannot be modified easily by the developer.

There was no reason to get rid of the convenient script. Most developers
who are not in love with autoconf fail to remember that autoreconf
invocation, therefore it is better to have something working in place.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

There was a possible buffer overflow in rfbFileTransferOffer message when
processing the FileTime.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Fixing 2 security issues

Otherwise the sources from a 'make dist' package wouldn't compile.

This change kinda got lost with the last commit re-splitting.

Autotools fix revisited.

.dirstamp, OTOH, is to be expected in several subdirectories.

 - no longer applicable: use autoreconf -fiv

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

A forgotten `#ifdef WIN32` broke UNIX build.

More MSVC adjustments, now focuses on the libvncserver

We also do not need the conversion between UNIX values to Windows values in the RTF_FIND_DATA struct, as we already are on windows.

The additional compat_mkdir function was not necessary at all.

`windows.h` is referring to `winsock.h` (unless the `WIN32_LEAN_AND_MEAN` is defined).
The structs used in this header are defined in `winsock2.h` or in `winsock.h`, but we are using Winsock2 of course!
So we have to include winsock2.h and refrain from including windows.h here

Basically taken from https://github.com/danielgindi/FileDir with some adjustments

Passing NULL to sprintf() would most likely crash the program.

`strings.h` and `resolv.h` are not available on MSVC, and some POSIX functions are renamed or deprecated

For all of those missing/deprecated POSIX functions, we just add a macro mapping to the _underscored version of MSVC.