"Constant Table" is misleading

[plobsing]

There are multiple senses of constant when it comes to Parrot:

• an item declared as const in the source
• an item that is readonly
• an object whose lifetime is eternal
• an item whose reference does not change (but whose dereferenced value may change)
• ...

These differing senses confound us when discussing or reasoning about something refered to as "constant". Therefore, we should drop the use of the term constant where possible, and "constant table" is one place I think we could.

Various alternatives have been proposed:

• object table
• pmc table (string table for strings, num table for nums)
• object pool
• packfile store
• packfile $x (always be explicit about the packfile)

More suggestions are welcome.