Fix spelling errors

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

modules/libcom/src/timer/timerQueue.cpp

@@ -148,7 +148,7 @@ double timerQueue::process ( const epicsTime & currentTime )
         }
 
         //
-        // only restart if they didnt cancel() the timer
+        // only restart if they didn't cancel() the timer
         // while the call back was running
         //
         if ( this->cancelPending ) {