Added accompanying Allocator and operators for the Pool.
Initial work at dr-grep. Runtime value creation and evaluation still to
come.
Updated CXXFLAGS for apps.
Initial implementation of Expr::eval for all Expr types except attribute
access. Separated type cast functions from store processing functions at
the lexeme level.
Added the "len" function and support for stores. Added support for
top-level return values from a Value object. Store enumeration
functions still to come.
Added helper classes for using C strings as keys to a
std::unordered_map.
Cleaning up the distinction between different function types and
different variable types.
Corrected missing "explicit" on PoolAllocator.
Fixed extra token consumption when parsing functions. Corrected memory
leak in FunctionExpr with internal std::vector not using PoolAllocator.
Added support for annotation processing.