MIR Serialization: use correct line and column numbers for LLVM IR errors.

This commit translates the line and column numbers for LLVM IR
errors from the numbers in the YAML block scalar to the numbers 
in the MIR file so that the MIRParser users can report LLVM IR 
errors with the correct line and column numbers.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10108

llvm-svn: 238576