1) Build static versions (flif and flif-dec)
2) Add "-mavx" for Win32 builds using GCC.  That is necessary for i686 binaries:

The ABI for passing parameters with 16-byte alignment has changed in GCC 4.6

3( build dflif
4) Have the source files match what the makefile builds
5) Build gdk-pixbuf2 loaders (both as static and shared libraries)
6) add test for static flif library builds
7) add install for viewer, gdk-pixbuf2 loaders, flif and flic-dec libraries, manual pages, shared-mime info, .magic file, licenses, as well as the gif2flif and apng2flif scripts.
8) Unlike make, the CMakeLists files does NOT call update-mime-database, append stuff to the file packages /etc/magic, or gdk-pixbuf-query-loaders --update-cache.  This is deliberate because those should be done when installing on a user's system, not when building a binary package for redistribution using Pacman, rpm, or dpkg.

…be more cross-platofm.

Note that for MINGW-W64, I had to use __USE_MINGW_ANSI_STDIO 1

Which should help make it run even with older versioms of msvcrt.dll that didn't support the GNU stan dard macros.

Using __STDC_FORMAT_MACROS permits you to use he constant even from C++.

build/MSVC/getopt/getopt.c - fix GCC warnings about code misteknly indented to imply it was guarded when it wasn't.  GCC warns about such things.
CMakeLists.txt - use C compiler instead of C++ compiler.  Clang depreciates that and it was also preventing me from using macros from inttypes.h.
src/config.h - Rename UNUSED maco to FLIF_UNUSUSED.  Also added a FALLTHROUGH macro from Graphite2.
src/fileio.cpp, src/flif.cpp, flif-dec.cpp, flif-enc.cpp - adjust for macro rename
src/pixbuf-loaders.c - fix warnings about unsigned comparisons
viewflif - remove define for C++.  It should be compiled with the C compiler instead.  Rename UNUSED maco and rwork things so it can work with MINGW-W64 and MSC.  Use inttype.h macros when we can.
images.cpp - adjust for macro rename
flif-common.  Change define for DLL import to Win32 since this is a common Windows-specific thing.  Yes, ther
e is clang and GCC for Windows.
fliif-enc.h, flinf-inerface_enc.cpp - fix Clang error.  dllimport can not be used on a non-inline function.
flif_interface-private_common.hpp - dllexport and import ifdef changed to _WIN32
tools/test.c - fix warning about signed compares as well issues with using int and long.  In Win64, those do not grow to 64-bits.  In addition, I wanted to use 64-bit file functions for all Windows versions.