swift234

IRGen: Emit witness tables as exported symbols in -emit-sil-protocol-witness-tables mode.

SILGen eagerly produces witness tables for all of the conformances defined in the module, which is what we want in order to make them runtime-unique. Have IRGen follow suit. This should address a ton of radars about breakage with non-unique conformances once SIL witnesses are turned on. We will need some runtime machinery to handle witness tables with dependent fields, but since we currently ignore the associated type fields of witnesses, we can get away with emitting direct references to all witness tables for now.

Swift SVN r11608