Explicitly indicate inlining success/failure in PrintInlining

I occasionally look at inlining traces produced by PrintInlining (either the compile command or the global flag.

This trace contains messages for both inlining successes and failures, but it doesn't explicitly indicate whether inlining succeeded or failed. Instead, we have to interpret the information message to determine if inlining succeeded or failed.

I propose to explicitly indicate in the message produced by PrintInlining, whether inlining succeeded or failed. For instance with an additional +/- in the message.