code: language cleanup in comments

Based on the standards and guidelines we use for our documentation.

 - expand contractions (they're => they are etc)
 - host name = > hostname
 - file name => filename
 - user name = username
 - man page => manpage
 - run-time => runtime
 - set-up => setup
 - back-end => backend
 - a HTTP => an HTTP
 - Two spaces after a period => one space after period

Closes #14073

lib/easygetopt.c

@@ -42,7 +42,7 @@ static struct curl_easyoption *lookup(const char *name, CURLoption id)
       }
       else {
         if((o->id == id) && !(o->flags & CURLOT_FLAG_ALIAS))
-          /* don't match alias options */
+          /* do not match alias options */
           return o;
       }
       o++;