There's no legend explaining what symbols mean for supported end-points, but it seems to be following the same format at wgpu. This PR copies wgpu's legend.

* [glsl-in] Support anonymous global uniforms

Partly fixes #210

* [glsl-in] Handle anon global structs in fn prelude

* [glsl-in] consolidate tests

- remove simple lex test as was covered by others
- combine related tests to single function
- remove redundant prefix in test names

* [glsl-in] Consolidtae lex tests further

Complete expression/statement support in MSL, refactor conversion methods in WGSL, and remove Statement::Empty

* Added support for glsl core version up to 400

* Added 330 to the list supported versions

* Added links to all extensions and fixed a extension being wrongfully activated

* Cleanup and check for image formats

* Removed useless extension and location on layout

* Added support for external functions and fixed global names

* Typefier allow Scalars in distance and length

* Addressed comments

* Fixed extension appearing after body

* Fixed entry point not being generated

* Fix lexer operator issues (with tests)

* [glsl-in] Don't convet to string in lexer tests

* [glsl-in] cleanup lexer tests further

- Consolidate use statements

- Iterate lex directly, check for None at end

* [glsl-in] Add gl_VertexIndex

Refactor variable handling out of parser.rs

* [glsl-in] Fixes for gl_VertexIndex

- Make lookup_variable a method of Program

- Try to cleanup conditional logic

* [glsl-in] Error on gl_ builtin in wrong stage

Wrapped in glsl-validate feature

* Added generation of the texture mappings to the glsl backend

* Added a temporary workaround for the spirv shaders
Fixed some parts that were using vulkan glsl

* Made texture mapping not require a sampler

* Used interface to build the texture map

* Made global names mandatory except for sampler ones

* Addressed more comments

* Removed the temp fix for the spirv frontend

* Addressed the comments

* [glsl] Promote glsl-new to glsl

* [glsl-in] rename feature glsl > glsl-in

* [spv-out] Add initial Rosetta test

For now just check that spv-out succeeds

* [spv-out] Check spv output has len > 0

* Extended Interface to be used in more places

* Applied comments and added tests

* Removed the statement visitor

* Fixed remaining comments

* [glsl-new] Add jump statements

- continue
- break
- return
- discard

* [glsl-new] Fix clippy error for return statement

* [spirv-out] Move instructions to own module

* [spirv-out] Fix wrong function use of some instructions

* [spirv-out] Update instruction parameters

* [spirv-out] Update current instruction tests

* [spirv-out] Order current instruction tests

* [spirv-out] Add missing instruction tests

* [glsl-new] Update last exprs to ExpressionRule

Refactor out binary_expr to keep parser.rs 'small' and readable

* [glsl-new] Change binary_expr to method on Program

* [glsl-new] Make binary_expr a proper method