reporter: fix samples.SetLocationsLength

[florianl]

Fixes #262

[rockdaboot]

Can you explain why sample.SetLocationsLength(int32(len(traceInfo.FrameTypes))) is wrong?
Because it looks like that a location for every frame is added with loc := profile.LocationTable().AppendEmpty().

[florianl]

In theory, a stack trace should contain only frames of type native, kernel or some kind of interpreter. But with the option -send-error-frames artificial frames are added to the stack trace to report known (unwinding) error codes. As the error code for these special frames are encoded within message Location, it make sense to keep the current behavior, until there is an agreement to report these special information.