[boost] [multi-array] constructor bypass patch

From: Neal Becker (ndbecker2_at_[hidden])
Date: 2007-04-19 07:09:22

This proposed patch allows bypassing of default constructors.  This can be
important for high performance computing.

What this patch does:

1. Add an optional arg to 'allocate_space' to specify if element
construction is wanted
2. Add 'default_do_init' static constant, which is false for POD and for
std::complex<T>
3. Also bypass construction when the result is going to be immediately
overwritten (copy_n)

4. Add to 'allocate_space' and optional init value, which default to T(). 
The purpose is to allow for a multi_array constructor that specifies an
initial fill value.  This is another optimization and consistent with STL
containers.  However, I haven't figured out how to use this yet.