[SV 39851] Reinstate stack size limit for processes spawned via $(shell)
[SV 33134] Don't try to close stdout when it's already closed.
[SV 35248] Add --debug "n" flag to turn off current debug options.
[SV 39203] Don't set MAKEFLAGS when restarting.

We are restarting with the original command line flags, so if we set
MAKEFLAGS as well that will cause double flags.
[SV 39934] Verify jobserver FDs before something else uses them.
[SV 27374] Fatal immediately on unrecoverable fopen() errors.
[SV 31326] Enhance the info on static pattern errors.
Small cleanup defining MAKEFLAGS.
Release GNU Make version 3.99.91.
Avoid compiler warnings in output.c on MS-Windows.

 output.c [WINDOWS32]: Include windows.h and sub_proc.h, to avoid
 compiler warnings for CLOSE_ON_EXEC.
Fix a typo in a comment.