ddc-core-flow: backup non-ILP clustering: comment out test that gets different clustering
convert Flow directly to Salt, instead of Tetra.
ddc-core-simpl: lambda lifter for recursive functions. lift the knot up to the top level
ddc-core-flow: to salt: after lambda lifting, force forward any let-bound functions, as they must be partial applications.
ddc-core-flow: to-salt tweaks
ddc-core-flow: modify rules for forward before lower and rate

We don't need to force everything to forward, as rate inference will
just treat anything that isn't a vector op as an external.
ddc-core-flow: prep forward and rate forward are very different
add .dcf compilation support
fix #337: LLVM output now supports NameExts.
ddc-core-flow: add sgenerate# to lower transform
ddc-core-flow: runProcess0# etc take a size
ddc-core-llvm: add units and fix boolean literals
ddc-core-salt: convert units from lite to salt, make C conversion handle units
ddc-core-flow: convert tuples
ddc-core-llvm: sanitize name of local variables (was not happening in scrutinee)
ddc-core-flow: to-salt: add truncation of vectors
fix #333: parsers were silently discarding leftover input. modified base runTokenParser to require EOF. had to fix a few test cases with extra close parens, too
fix #338: allow lexer to start vars with '_'.

lexer was treating "_foo" as two separate tokens, but one salt transform
was creating a new function called "_main". this worked fine until it
was pretty printed and then parsed again.
I've changed the language lexers to support variables starting with '_'
and lowercase letters.
add note: which files to touch when changing DDC_FLOW_USE_LINEAR_SOLVER make configuration
fix #336: Snip;Flatten;Forward no longer removes original names.

added a special case to flatten:

> let x = (let ^ = def in ^0)
>  in rest

now becomes

> let x = def
>  in rest

instead of the previous

> let ^ = def
> let x = ^0
>  in rest

this plays nicer with Forward transform, letting the transformed program
keep the original variable names where possible.