Put quote marks around strings, due to a change in how tokenization works.

Only when operations stray outside the 8/16-bit storage-capabilities
are the general (pure 8/16-bit) capabilities needed.

 Match https://github.com/KhronosGroup/GLSL/pull/22

Tracks https://github.com/KhronosGroup/GLSL/pull/22.

Fixes #854. But, only good if we are not trying to use the same
texture for both shadow and non-shadow constructors.

Force the type of the texture to have 'shadow' set when it is
constructed with a samplerShadow.

Fixes #1309.

This is one step in providing full linker functionality for creating
correct SPIR-V from multiple compilation units for the same stage.
(This was the only remaining "hard" part. The rest should be simple.)

When constructing a matrix from another matrix with smaller dimensions,
there's no need to extract the scalars out of columns and rebuild the
resulting matrix from scalars - instead, we can just construct shorter
vectors with OpShuffle and combine them to the final result.

This keeps the common casts such as mat3(mat4) in vector registers,
which may improve performance for some GPUs, and cleans up output of
translation tools like SPIRV-Cross.

Fixes #1412.

These introduce limited support for 8/16-bit types such that they can only be accessed in buffer memory and converted to/from 32-bit types.

Contributed from Khronos-internal work.

(If there is a bias issue, we need to discover what it is.)

This results in better error recovery, including fewer
crashes on badly formed PP input.

This reverts commit ebec9094.

Khronos decided glslang was originally correct, and the specifications
are incorrect.

1e-323 was flushed to zero.
1e-308 is also flushed to zero.
Use 1e-307 instead, which still satisfies the test intent.

Fixes #1400

The major version number was bumped in the previous commit to support
this.