swift234

IRGen: Emit failure blocks individually

Reapply commit r24722.

The original commit did not break the build. There appears to be an issue in
CoreAutomation (an iOS test failed with empty output). Follow up builds with
the original commit in succeeded.

Also apply Dimitri's patch to make the test condfail.sil portable.

Original message:

This significantly improves debugging experience as failures such as overflow
can be mapped back to a source line.

Code size impacts I measured on PerfTestSuite and libswift*.dylib was
neglectable.

__text section size increase:

  0.24% bin/PerfTest_O
  0.01% bin/PerfTest_Onone
  0.20% libswift*.dylib

rdar://19118593

Swift SVN r24725