Fix Bug 20400

Summary:
http://llvm.org/bugs/show_bug.cgi?id=20400

The default triple of i686-pc-linux-gnu for 32 bit linux targets is compatible
but not necessarily identical to the inferior binaries.

Applying Azat Khuzhin's solution of using ArchSpec::IsCompatibleMatch() instead
of ArchSpec::IsExactMatch() when comparing ObjectFile and Modules architecture.

Reviewers: vharron

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D7897