Reland A new option -print-on-crash that prints the IR as it was upon entering...

Reland A new option -print-on-crash that prints the IR as it was upon entering the last pass when there is a crash.

Summary:
The IR is saved in its print form before each pass is started and a
signal handler is registered.  If the compilation crashes, the signal
handler will print the saved IR to dbgs().  This option
can be modified using -print-module-scope to get the IR for the complete
module.  Filtering options can be used to improve performance by limiting
which passes (or functions) save the IR.  Note that this option only works
with the new pass manager.

Author: Jamie Schmeiser <schmeise@ca.ibm.com>
Reviewed By: aeubanks (Arthur Eubanks) yrouban (Yevgeny Rouban)
Differential Revision: https://reviews.llvm.org/D86657