[PATCH v3 28/33] tracing: Add 'last error' error facility for hist triggers

With the addition of variables and actions, it's become necessary to provide more detailed error information to users about syntax errors. Add a 'last error' facility accessible via the erroring event's 'hist' file. Reading the hist file after an error will display more detailed information

[PATCH v3 28/33] tracing: Add 'last error' error facility for hist triggers

With the addition of variables and actions, it's become necessary to provide more detailed error information to users about syntax errors. Add a 'last error' facility accessible via the erroring event's 'hist' file. Reading the hist file after an error will display more detailed information