Split qstr into pools, and put initial pool in ROM.
Qstr's are now split into a linked-list of qstr pools. This has 2 benefits: the first pool can be in ROM (huge benefit, since we no longer use RAM for the core qstrs), and subsequent pools use m_new for the next pool instead of m_renew (thus avoiding a huge single table for all the qstrs). Still would be better to use a hash table, but this scheme takes us part of the way (eventually convert the pools to hash tables). Also fixed bug with import. Also improved the way the module code is referenced (not magic number 1 anymore).