Rewrite sampler to use Elisp hash-tables.

Rewrite sampler to use Elisp hash-tables.
* src/profiler.c: Remove filtering functionality.
(is_in_trace, Qgc): Remove vars.
(make_log, record_backtrace, Fsample_profiler_log):
Rewrite, using Elisp hash-tables.
(approximate_median, evict_lower_half): New functions.
(cpu_log): Rename from sample_log.
(cpu_gc_count): New var.
(Fsample_profiler_reset, Fmemory_profiler_reset): Remove.
(sigprof_handler): Add count to cpu_gc_count during GC, detected via
backtrace_list.
(block_sigprof, unblock_sigprof): Remove.
(gc_probe, mark_profiler): Remove functions.
(syms_of_profiler): Staticpro cpu_log and memory_log.

* lisp/profiler.el (profiler-sample-interval): Move before first use.
Change default to 1ms.
(profiler-entry=, profiler-backtrace-reverse, profiler-log-fixup-slot)
(profiler-calltree-elapsed<, profiler-calltree-elapsed>): Remove functions.
(profiler-entry-format): Don't use type-of.
(profiler-slot, profiler-log): Remove structs.
(profiler-log-timestamp, profiler-log-type, profiler-log-diff-p):
Redefine for new log representation.
(profiler-log-diff, profiler-log-fixup, profiler-calltree-build-1):
Rewrite for new log representation.
(profiler-calltree): Remove `elapsed' fields.
(profiler-calltree-count<, profiler-report-make-entry-part):
Remove gc special case.
(profiler-calltree-find): Use equal.
(profiler-calltree-walk): Remove `args'; rely on closures instead.
(profiler-calltree-compute-percentages-1): Remove; inlined.
(profiler-calltree-compute-percentages): Simplify.
(profiler-report-log, profiler-report-reversed)
(profiler-report-order): Use defvar-local.
(profiler-report-line-format): Remove `elapsed', do a bit of CSE.
(profiler-report-mode-map): Remove up/down bindings.
(profiler-report-make-buffer-name): Simplify by CSE.
(profiler-report-mode): Remove redundant code.
(profiler-report-expand-entry, profiler-report-collapse-entry):
Use inhibit-read-only.
(profiler-report-render-calltree-1): Simplify by CSE.
(profiler-reset): Rewrite for new subroutines.
(profiler--report-cpu): Rename from sample-profiler-report.
(profiler--report-memory): Rename from memory-profiler-report.

* src/alloc.c (Fgarbage_collect): Record itself in backtrace_list.
Don't set is_in_trace any more.  Don't call mark_profiler.
Only call gc_probe for the memory profiler.
(syms_of_alloc): Define Qautomatic_gc.

* src/lisp.h (SXHASH_COMBINE): Move back to...
* src/fns.c (SXHASH_COMBINE): ...here.

* src/xdisp.c (Qautomatic_redisplay): New constant.
(redisplay_internal): Record itself in backtrace_list.
(syms_of_xdisp): Define Qautomatic_redisplay.

* .dir-locals.el (indent-tabs-mode): Remove personal preference.