fix (unreported): Weld Modifier: possible use of uninitialized variable

Fix T74495: Shrink/Fatten gives strange results with Individual Origins

The island `axismtx` is only necessary in some transform modes.

In the case of `Shrink/Fatten`, the calculated `axismtx` brings an
undesirable result.

This commit rearrange the struct `TransIslandData` in order to
calculate and reference only the arrays that will be used for each
transform mode.

Differential Revision: https://developer.blender.org/D7305

Fix customdata interpolation being done multiple times in Weld Modifier

Cleanup: Organize Weld Modifier in alphabetical order

Fix T74588: Weld Modifier: Vertex colors and UVs get incorrect values

Edit Curve: Improve Curve extrude

The original code has two logics, extrude the end points or duplicate points (making new splines).
Now all the logic has been redone by extruding contiguous selected segments.

Fix T47169

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D6982

Fix T74969: Crash in gpencil edit mode

Result of poor shader pre-processing on Intel HD 4000 drivers

Fix missing text input on Windows with certain keyboard layouts

Events for keys specific to certain keyboard layouts unknown to Blender
were ignored. Now pass them along as unknown key events for which we
can still handle text input, like we already do for Linux and macOS.

Differential Revision: https://developer.blender.org/D7229

Cleanup: Silence warnings

```
...gpu_texture.c(466,7): warning C4555: result of expression not used
...gpu_texture.c(559,7): warning C4555: result of expression not used
...gpu_texture.c:1205:72: warning: pointer targets in passing argument 4 of ?glGetTexLevelParameteriv? differ in signedness [-Wpointer-sign]
```

GPU: Estimate a better value for the memory used

This commit adds a `mipmaps` member to the `GPUTexture` struct and also
computes to the memory used by these mipmaps and the memory used for
textures that are created from an external bindcode.

So it solves the following inconsistencies:
- The memory value for mipmaps was not being computed.
- As `GPU_texture_from_bindcode` didn't call
`gpu_texture_memory_footprint_add`, it brought inconsistencies to the
value of the used memory, especially when the texture is freed.

Differential Revision: https://developer.blender.org/D3554