IR gen: new stream buffer allocation scheme and ABI
remove the "<expr>{.}" syntax in favour of increased type-constraints
test: matrix multiplication
examples: matrix multiplication: update comments
test: matrix multiplication: cosmetics
frontend: keep all llvm-related stuff in the IR generator
IR gen: implement built-in math functions
cmake: streams module
examples: spectral flux: re-enable use of built-in math functions
IR gen: fix slicing: convert index from 1-based to 0-based.
examples: spectral-flux: update a comment