Various fixes and enhancements for tracing

This patchset applies on latest -tip (and normally against latest Steven's tracing tree).

_ tracing/ftrace: Fixes unexpected -EINVAL when longest tracer name is set _ tracing/ftrace: Change the type of the init() callback
_ tracing/branch-tracer: Fix a trace recursion on branch tracer
_ tracing/function-return-tracer: Support for dynamic ftrace on function return tracer

The first and the third are bug fixes and the others are submitted for purposes on improvement for tracing and the function return tracer.
Note that I kept the "return" name for the names used in the last patch because we haven't yet decided what could be the better name. But once we find it, I will change the name of data structures and functions used by this tracer.

applied to tip/tracing/ftrace,

applied to tip/tracing/branch-tracer,

applied to tip/tracing/function-return-tracer.

thanks Frederic!

ok.

Ingo