Cmake Fix broken changes related to /scripts/cmake/ change in 1.6.41

[danoli3]

Changes to CMakeLists.txt

Critical Bug as 1.6.41/1.6.42/1.6.43 cannot compile with this change :

Moved the CMake files (except for the main CMakeLists.txt) to scripts/cmake and moved the list of their contributing authors to scripts/cmake/AUTHORS.md

• Tested 1.6.41 - Fails to compile
• Tested 1.6.42 - Fails to compile
• Tested 1.6.43 - Fails to compile

After proposed changes linking code to correct folder Building now!

Added emscripten WASM target also now works

[danoli3]

Also congrats on finally getting the pnggroup switched over!

Finally can contribute, Long Live PNG @glennrp

[ctruta]

Many thanks. As I wrote in issue #547, I will apply your fix, but I will make a bunch of modifications of my own on top of it.

May I please kindly ask you to submit a separate PR for the Emscripten port? I may integrate it in the upcoming 1.6.43, or I may not, but I don't want it to be lost. That thing is a completely different issue, and I plan on closing this one after I apply and integrate the CMake fix.

[danoli3]

Squashed that commit and making other PR for emscripten wasm

[ctruta]

Thanks again @danoli3, I integrated your commit in trunk, even though GitHub doesn't seem to realize it. Both #546 and #547 should be fixed now.