[IR] AutoUpgrade ModuleFlagBehavior for PIC and PIE level

Summary:
From r303590, ModuleFlagBehavior for PIC and PIE level is changed from
Error to Max. This will cause bitcode compatibility issue when linking
against a bitcode static archive built with old compiler.
Add an auto-ugprade path to upgrade the the ModuleFlagBehavior in the
old bitcode to match the new one so IRLinker can link them.

Reviewers: tejohnson, mehdi_amini, dexonsmith

Reviewed By: dexonsmith

Subscribers: hans, llvm-commits

Differential Revision: https://reviews.llvm.org/D36556

llvm-svn: 311387