Most errors found with:
codespell -L cach,thst,odly,aslo,parm,parms,inpu,ges,prset,pevent,ptd,pring,valu,noo,noe,ned,inout,ro,siz,froms,nd,fo,singl,sart,multy,tthe,allong,ment,inate,nodel,tring,alse,ture,thi,wille,numer
Some more manually found (its -> it's)
c++20: Do not use apostrophe (e.g. can't) in unquoted #error message
caProto.h was using IPPORT_USERRESERVED but not including itself,
meaning there was an order dependency of header inclusion when using
this header. Now there shouldn't be.
Also, RTEMS wasn't defining IPPORT_USERRESERVED, so that definition
has been added.
In some cases the license-identification header was missing,
so I added that as well. Replaced the remaining headers that
specifically identified "Versions 3.13.7 and higher".
Makefiles and the build system were deliberately excluded.
