Initial prototype for an easier way to impose boundary conditions in Halide.
Fix C++11 arbitrary number of arguments support.
Move functionality to BoundaryConditions namespace.

Add a paltry smattering of comments barely sufficient to start
feedback process.
Merge branch 'master' into boundary_conditions

Conflicts:
	Makefile
Add some explanatory comments relating mechanism to GL texture wrapping modes.
Merge branch 'master' into boundary_conditions
Changed to passing Exprs by value in stead of const reference to be
consistent with style elsewhere.

Added const qualifier to Var's cast to Expr operator per a report of
compiler errors from Takayuki Muranushi. It seems like the correct
thing and that it was missing was an oversight, but perhaps I'm
missing something.
Add support for applying boundary conditions to ImageParam, Image<T>,
and similar types.

Add support for automatically applying boundary conditions at the
bounds of ImageParam, Image<T>, and similar types.

Add std::vector<Expr> and std::vector<Var> overloads for operator() in
Image<T> and ImageParam types.
Fix boundary conditions applied to ImageParam and Image<T> to use
implicit variable names (_0, _1, _2, etc...)
Merge pull request #357 from halide/boundary_conditions

Boundary conditions