Improve InvalidCString runtime error message description.
Add defines to control whether or not the trace viewer shows explanations or
process-wide states (temporary for testing).
Add dynamic memory allocations to SeeC-Clang Mapped states.

Each dynamic memory allocation is represented by a seec::cm::MallocState. This
class allows clients to get the allocation address and size, the allocating
llvm::Instruction, and the allocating clang::Stmt.

All current dynamic memory allocations can be retrieved using
seec::cm::ProcessState's getDynamicMemoryAllocations() method.

The unmapped MallocState now records the llvm::Instruction responsible for the
allocation (accessible using getAllocator()).
Merge branch 'master' of https://github.com/mheinsen/seec