Fix inline_vars_push() - need to zero the new state
Split out variadic and unspec-arg function checks
Test for indirect call inlining
Disable argument retain check on call gen
Handle (possibly mutually) recursive inlining
Another inline recursion test
Test inability to inline certain functions
Change inline error message CHECKs in tests
Old-func -> prototype func for inline test
Prototype decls link to their implementation (for forward-inlining)
Move inline codegen check to the gen-stage

This allows for exact reporting on whether a function call can be
inlined or not.
Recursive always-inline test can now check forward-inlines
Updated TODO_INLINE
Example of stack-allocation TODO for inlining
Notes on DWARF output for inline functions