Fix error calling function in package body recursively
Improved checking for functions with default arguments
Tweak to how contexts are represented

Conflicts:
	src/simp.c
	test/simp/ffold.vhd
	test/test_simp.c
Fix build after previous commit

Conflicts:
	src/simp.c
Fix serialising context_t structures
New constant folding module
Tweaks to evaluation code
Tidy up eval module
Fix eval_ function naming
Replace function declaration references with function bodies
Replace unit_t with tree_t
Improve dumper for physical types
Force type of unit decl multiplier
Reorder operations in main to do all parsing and checking before simplification
Simplification for some constant type conversions
Move some shared functions to common.c