Bitcode reader: Inline readAbbreviatedField in readRecord and move the...

Bitcode reader: Inline readAbbreviatedField in readRecord and move the enclosing loop in each case (NFC)

Summary: This make readRecord 20% faster, measured on an LTO build

Reviewers: rafael

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17911

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 262811