cleanup: comment typos

Spotted by 'codespell'

Closes #4957

lib/cookie.c

@@ -1048,7 +1048,7 @@ Curl_cookie_add(struct Curl_easy *data,
 
         *clist = *co;  /* then store all the new data */
 
-        free(co);   /* free the newly alloced memory */
+        free(co);   /* free the newly allocated memory */
         co = clist; /* point to the previous struct instead */
 
         /* We have replaced a cookie, now skip the rest of the list but

lib/setopt.c

@@ -2288,7 +2288,7 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, va_list param)
 
   case CURLOPT_SSH_KEYFUNCTION:
     /* setting to NULL is fine since the ssh.c functions themselves will
-       then rever to use the internal default */
+       then revert to use the internal default */
     data->set.ssh_keyfunc = va_arg(param, curl_sshkeycallback);
     break;
 

lib/vssh/libssh.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 2017 - 2019 Red Hat, Inc.
+ * Copyright (C) 2017 - 2020 Red Hat, Inc.
  *
  * Authors: Nikos Mavrogiannopoulos, Tomas Mraz, Stanislav Zidek,
  *          Robert Kolcun, Andreas Schneider
@@ -1586,7 +1586,6 @@ static CURLcode myssh_statemach_act(struct connectdata *conn, bool *block)
             return CURLE_BAD_DOWNLOAD_RESUME;
           }
         }
-        /* Does a completed file need to be seeked and started or closed ? */
         /* Now store the number of bytes we are expected to download */
         data->req.size = size - data->state.resume_from;
         data->req.maxdownload = size - data->state.resume_from;

lib/vssh/libssh2.c

@@ -2381,7 +2381,6 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
             return CURLE_BAD_DOWNLOAD_RESUME;
           }
         }
-        /* Does a completed file need to be seeked and started or closed ? */
         /* Now store the number of bytes we are expected to download */
         data->req.size = attrs.filesize - data->state.resume_from;
         data->req.maxdownload = attrs.filesize - data->state.resume_from;

src/tool_cb_hdr.c

@@ -109,7 +109,7 @@ size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
       size_t etag_length = 0;
 
       etag_h = ptr;
-      /* point to first occurence of double quote */
+      /* point to first occurrence of double quote */
       first = memchr(etag_h, '\"', cb);
 
       /*
@@ -127,7 +127,7 @@ size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
         first++;
       }
 
-      /* point to last occurence of double quote */
+      /* point to last occurrence of double quote */
       last = memchr(first, '\"', cb);
 
       if(!last) {