Added subdir-objects option to configure.ac.
Fixed up index string code.
Fixed up index string code.
Added hashing and comparison helper procedures for strings.
Moved IsInt32IdString implementation to string code instead of vm_helpers code.  Fixed up string interface so that string-arguments-for-reading take the length after the string pointer instead of before.
Added IsInt32IdString variant for Values.  Optimized it for LinearStrings.
Fixed bugs in ImmString implementation in value.cpp