4.19-stable patches

4.19-stable patches

added patches:
	btrfs-add-missing-mutex_unlock-in-btrfs_relocate_sys_chunks.patch
	docs-kernel_include.py-cope-with-docutils-0.21.patch
	serial-kgdboc-fix-nmi-safety-problems-from-keyboard-reset-code.patch
	string.h-add-str_has_prefix-helper-function.patch
	tracing-add-unified-dynamic-event-framework.patch
	tracing-consolidate-trace_add-remove_event_call-back-to-the-nolock-functions.patch
	tracing-generalize-hist-trigger-onmax-and-save-action.patch
	tracing-have-the-historgram-use-the-result-of-str_has_prefix-for-len-of-prefix.patch
	tracing-refactor-hist-trigger-action-code.patch
	tracing-remove-unnecessary-var_ref-destroy-in-track_data_destroy.patch
	tracing-remove-unneeded-synth_event_mutex.patch
	tracing-simplify-creation-and-deletion-of-synthetic-events.patch
	tracing-split-up-onmatch-action-data.patch
	tracing-use-dyn_event-framework-for-synthetic-events.patch
	tracing-use-str_has_prefix-helper-for-histogram-code.patch
	tracing-use-str_has_prefix-instead-of-using-fixed-sizes.patch