[examples][shaders_raymarching] Add raymarching.fs for GLSL120

[CDM15y]

Raymarching example shader ported to glsl 1.20, and tested on Intel Mobile 4 Series Chipset Integrated Graphics Controller

[CDM15y]

title change and no pull?

[raysan5]

@CDM15y pull requires verification and validation. And it requires time.

[raysan5]

@CDM15y Added some review comments.

[raysan5]

I'm afraid I'm closing this PR, no reviews have been made.

[CDM15y]

@raysan5 What do you mean by reviews? sorry, I'm a beginner to pull requests and Github in general.
This is just the GLSL 330 shader, modified to work on GLSL 120 for desktop GL to work on Raspberry Pi and old PCs.

[raysan5]

@CDM15y Some reviews were requested, the changes should be added as additional commits to this PR but were not, in any case, this file is almost the same as glsl100 version, only 2 lines change

[CDM15y]

I didn't realize there was a glsl100 version, this was based off the 330 version. should I reopen a pull request and add the changes as additional commits?

[raysan5]

@CDM15y ok, reopened 🙂

[CDM15y]

#version 120 is correctly specified for GLSL 120.

use varying and attribute instead of in and out to match GLSL 120 syntax.

use gl_FragColor instead fragColor to to match GLSL 120 standards.

Moved the license to the top of the code to improve readability.

[raysan5]

@CDM15y thanks for the addition