misc: fix typos in docs and comments

No user facing output from curl/libcurl is changed by this, just
comments.

Closes #7747

docs/KNOWN_BUGS

@@ -1018,7 +1018,7 @@ problems may have been fixed or changed somewhat since this was written!
 
 15.4 build docs/curl.1
 
- The cmake build doesn't create the docs/curl.1 file and therefor must rely on
+ The cmake build doesn't create the docs/curl.1 file and therefore must rely on
  it being there already. This makes the --manual option not work and test
  cases like 1139 can't function.
 

docs/libcurl/opts/CURLOPT_SSL_ENABLE_ALPN.3

@@ -22,7 +22,7 @@
 .\"
 .TH CURLOPT_SSL_ENABLE_ALPN 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
 .SH NAME
-CURLOPT_SSL_ENABLE_ALPN \- Application Layer Protocol Negotation
+CURLOPT_SSL_ENABLE_ALPN \- Application Layer Protocol Negotiation
 .SH SYNOPSIS
 #include <curl/curl.h>
 

lib/curl_sasl.c

@@ -272,7 +272,7 @@ static CURLcode build_message(struct Curl_easy *data, struct bufref *msg)
   char *base64;
   size_t base64len;
 
-  if(!Curl_bufref_ptr(msg))             /* Empty mesage. */
+  if(!Curl_bufref_ptr(msg))             /* Empty message. */
     Curl_bufref_set(msg, "", 0, NULL);
   else if(!Curl_bufref_len(msg))        /* Explicit empty response. */
     Curl_bufref_set(msg, "=", 1, NULL);

lib/http_aws_sigv4.c

@@ -321,7 +321,7 @@ CURLcode Curl_output_aws_sigv4(struct Curl_easy *data, bool proxy)
 
   /*
    * Google allow to use rsa key instead of HMAC, so this code might change
-   * In the furure, but for now we support only HMAC version
+   * In the future, but for now we support only HMAC version
    */
   str_to_sign = curl_maprintf("%s4-HMAC-SHA256\n" /* Algorithm */
                               "%s\n" /* RequestDateTime */

lib/http_proxy.c

@@ -207,7 +207,7 @@ static void connect_done(struct Curl_easy *data)
     Curl_dyn_free(&s->rcvbuf);
     Curl_dyn_free(&s->req);
 
-    /* retore the protocol pointer */
+    /* restore the protocol pointer */
     data->req.p.http = s->prot_save;
     s->prot_save = NULL;
     infof(data, "CONNECT phase completed!");

src/tool_getparam.c

@@ -1430,7 +1430,7 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
           char *enc = curl_easy_escape(NULL, postdata, (int)size);
           Curl_safefree(postdata); /* no matter if it worked or not */
           if(enc) {
-            /* replace (in-place) '%20' by '+' acording to RFC1866 */
+            /* replace (in-place) '%20' by '+' according to RFC1866 */
             size_t enclen = replace_url_encoded_space_by_plus(enc);
             /* now make a string with the name from above and append the
                encoded string */