[lit] Fix several tests that fail when using Python 3 or on Windows

Summary:
1) In logtest.cpp, the name of the file that is reported is not always capitalized, so split the comparison to validate the file (case insensitive) and function (case sensitive) separately
2) Update the gdb remote client tests to work with Python 3. In Python 3, socket sends/receives data as bytes rather than byte strings. This also updates the usage of .hex() - this is no longer available in Python 3, so use hexlify instead

Reviewers: asmith, labath, zturner

Reviewed By: labath

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D46773

llvm-svn: 332293