Each collector were a slot_visitor containing a gc_workhorse containing
a policy class. This commit removes the gc_workhorse and the policies
and instead "inlines" the common code in the collector bodies. So there
is more code duplication, but the control flow doesn't "jump around" so
much so it is easier to understand. It also makes the nursery gc faster
because its collection code can be optimized better without the
workhorse/policy system.
clang-format doesn't recognize casts to non-pointer/non-template types
so it winds up adding a space between the right paren and the expression
and then failing to recognize prefix operators in the process
(e.g. foo = (cell) & bar; should be foo = (cell)&bar;). This commit
manually fixes up the major cases (fixnum, cell, all types ending in _t).
Björn Lindqvist
Erik Charlebois
Slava Pestov