WebP broken and some other plugins.

[tompaynter03]

In Plugin.cpp the index of each plugin is important as they are hard coded in the FREE_IMAGE_FORMAT enum.

If any of the #if INCLUDE_LIB_... conditions are false it changes the order of the plugins after it breaking those plugins.

In my case INCLUDE_LIB_OPENEXR was off as a result WebP support was broken.

			#if INCLUDE_LIB_OPENEXR
			s_plugins->AddNode(InitEXR);
			#endif
			s_plugins->AddNode(InitJ2K);
			s_plugins->AddNode(InitJP2);
			s_plugins->AddNode(InitPFM);
			s_plugins->AddNode(InitPICT);
			#if INCLUDE_LIB_RAW
			s_plugins->AddNode(InitRAW);
			#endif
			#if INCLUDE_LIB_WEBP
			s_plugins->AddNode(InitWEBP);
			#endif
			#if INCLUDE_LIB_JXR
#if !(defined(_MSC_VER) && (_MSC_VER <= 1310))
			s_plugins->AddNode(InitJXR);
#endif // unsupported by MS Visual Studio 2003 !!!
			#endif

I have kludged a fix together here to replace the missing plugins with the BMP plugin, there is certainly a better way to handle this but its working for my use case.
tompaynter03@5f13b7f