Minor enhancements to the MinGW+Msys build scripts.

Makefile now creates a zipfile containing the DLLs.

Resulting DLL no longer contains a version number in its name.  (The
Windows convention is to ship the DLL with the program using it.
Versioning the name just makes it harder for scripts to find the DLL.)

Tweaked the README a bit.
Bug fix: GD DLL rename hadn't been propagated everywhere.
MSys Makefile fix

Now adds the -static-libgcc flag.  This removes libgcc as a dependency.
MSys Makefile now statically links libgd.dll to libiconv.

This reduces dependencies but merges in LGPL code.  You can also
dynamically link it by commenting and uncommenting two lines.
Fix gdImageSetInterpolationMethod with GD_DEFAULT

As we have "im->interpolation_id = id;" after the switch
new example "resize"
Fix artefact in gdImageScale using GD_BILINEAR_FIXED

See https://bugs.php.net/66887 for sample image
and examples/resize.c to test.
Add overlay and multiply effects to gdImageSetPixel
add tests for layer effects
Fix buffer overrun from long font search path

MAXPATHLEN is set to 256 (on some systems), and DEFAULT_FONTPATH is longer
than this (on some systems). The sprintf() to path[MAXPATHLEN] thus
resulted in a buffer overrun when in some circumstances (also,
fontsearchpath is in the control of the environment, so this could be
triggered on any platform).
Remove wrong license headers. Based on http://www.paulbourke.net/dataformats/tga/
CVE-2014-2497, NULL pointer dereference, fix #126
Merged in ttoohey/gd-libgd/bugfix/font_path_overrun (pull request #19)

Fix buffer overrun from long font search path
Merged in ttoohey/gd-libgd/layout-effect (pull request #18)

Overlay and multiply effects for gdImageSetPixel
Merged from the upstream.

Specifically, 'master' of https://bitbucket.org/libgd/gd-libgd
Changed path to libiconv in msys Makefile.

The path is now relative to /c/.  Previously, it assumed that
/mingw was mounted, a recommended practice that is not enabled
by default.
Start work on nmake makefile
Get makefile almost working
Added strcasecmp implementation, now creates a .dll
Rename Makefile.gd and add some notes