[Reproducer] Include the this pointer in the API log.

The new centralized way of doing API logging through the reproducer
macros is lacking a way to easily correlate instances of API objects.
Logging the this pointer makes that significantly easier. For methods
this is now always passed as the first argument, similar to the self
argument in Python.

This patch also adds a test case for API logging, which uncovered that
we were not quoting strings.

Differential revision: https://reviews.llvm.org/D67538

llvm-svn: 371885