Suppress -Wmissing-braces warning when aggregate-initializing a struct with a...

Suppress -Wmissing-braces warning when aggregate-initializing a struct with a single field that is itself an aggregate.

In C++, such initialization of std::array<T, N> types is guaranteed to work by
the standard, is completely idiomatic, and the "suggested" alternative from
Clang was technically invalid.

llvm-svn: 314838