[docs] Import of additional member documentation that contain generic parameteres
[docs] documentation import for 'returns' elements.
[counters] Edit according to Kumpera review
Merge pull request #1020 from ludovic-henry/pr7-system-counters

[counters] Add system counters
[profiler] Emit statistical samples at 1 second intervals and fix race condition.
[profiler] In mprof-report fix handling of the time filter when starting from 0 (xambug #11904).
[profiler] Filter more event types in mprof-report based on time (more xambug #11904).
[mprof-report] Fix bug where no counters would be printed if --verbose or --counters-sort=category were not passed
[profiler] Add managed backtrace support to sampling mode for the signal-based impl.
[sdb] Avoid stack overflows when a boxed vtype recursively references itself using fields. Fixes #18914.
[mprof-report] Fix crash in case no counters values were sampled because of too short run time
[Mono.Debugger.Soft] Using cached GetParameters when fetching GetLocals
[Mono.Debugger.Soft] Caching tokens resolving
Clean up the usage of FILETIME structures, avoid accessing them as gint64 since that would lead to alignment problems. Hopefully fixes #19739.
[bcl] Fix Process.PrivateMemorySize64 on osx, we now return task_baic_info.resident_size. Fixes #19738.
[System.IO.KeventWatcher] Introduce enums with the KEvent flags and constants

This merely introduces a more readable version of some of the constants that
were hardcoded on the source code.

There is a suspect value "20" that was on the original source code, that
stands for VNodeLink and VNodeExtend, but perhaps the original author
meant to say VNodeRename.   In any case, it seems like we should catch all
of them (except for Revoke).
[boehm] Implement mono_gc_get_restart_signal.
[sgen] Implement mono_gc_get_restart_signal.
[gc] Add mono_gc_get_restart_signal.
[jit] Unblock more critical signals at startup.

Unblock the GC suspend/restart signals and SIGCHLD. Those are required to make the GC
and process watching work.

The SIGCHLD issue was found on mod_mono that fork a process with that signal blocked.

The GC signals are been preemptively unblocked as we can never know what sort of sig mask
we'll start with.