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/test/epicsAtomicPerform.cpp

@@ -237,7 +237,7 @@ private:
 // function and also increment an integer word. The
 // epicsInterruptIsInterruptContext function is an
 // out-of-line function implemented in a shareable library
-// so hopefully it wont be optimized away.
+// so hopefully it won't be optimized away.
 template < class T >
 inline void OrdinaryIncr < T > :: run ()
 {