[array] Overloaded function make_array() to create initialized arrays.

This is especially useful when an array is needed to initialize a class
member.

This uses a statement like

  array<T, 2> result = { t0, t1 };

to initialize the array.  This is correct and explicitly allowed by the
upcoming standard.  Unfortunately g++ warns about this with -Wmissing-braces
(which is implied by -Wall) because this relies on brace elision.  The report
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25137> has been filed more than
five years ago, but so far not much has happened.

[[Imported from SVN: r6328]]