ComputeBridge: Remove a load of redundant system code from fcpp - getting in the way of figuring out how it works.
ComputeBridge: Lots of changes to kick-off HLSL support.
* Removed custom platform prologue headers and replaced them with new platform headers in cbpp.
* HLSL detected positively instead of negatively.
* Split all_types into basic/extended sets.
* Moved all math/atomic stuff out of platform headers.
* Prevent double-include of headers with generated vs. direct-compile target languages.
* Added 4->3 and 3->2 conversion functions for vectors.
* Removed all the old cmp_ conversion functions.
* Vector construction now works for all languages.
ComputeBridge: Reenable local  includes.