Spelling cleanup.

No functional changes, just fixing minor spelling issues.

---

Most of these were identified from the command line by running:

  codespell \
    --ignore-words-list fpr,stati,keyserver,keyservers,asign,cas,iff,ifset \
    --skip '*.po,ChangeLog*,help.*.txt,*.jpg,*.eps,*.pdf,*.png,*.gpg,*.asc' \
    doc g13 g10 kbx agent artwork scd tests tools am common dirmngr sm \
    NEWS README README.maint TODO

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>

sm/certchain.c

@@ -558,7 +558,7 @@ find_up_search_by_keyid (ctrl_t ctrl, KEYDB_HANDLE kh,
           rc = -1;
           goto leave;
         }
-      /* Ready.  The NE_FOUND_CERT is availabale via keydb_get_cert.  */
+      /* Ready.  The NE_FOUND_CERT is available via keydb_get_cert.  */
     }
 
  leave:

sm/export.c

@@ -47,7 +47,7 @@ struct duptable_s
   struct duptable_s *next;
 
   /* Note that we only need to store 19 bytes because the first byte
-     is implictly given by the table index (we require at least 8
+     is implicitly given by the table index (we require at least 8
      bits). */
   unsigned char fpr[19];
 };

sm/fingerprint.c

@@ -158,7 +158,7 @@ gpgsm_get_short_fingerprint (ksba_cert_t cert, unsigned long *r_high)
 
 
 /* Return the so called KEYGRIP which is the SHA-1 hash of the public
-   key parameters expressed as an canoncial encoded S-Exp.  ARRAY must
+   key parameters expressed as an canonical encoded S-Exp.  ARRAY must
    be 20 bytes long.  Returns ARRAY or a newly allocated buffer if ARRAY was
    given as NULL.  May return NULL on error.  */
 unsigned char *

sm/sign.c

@@ -333,7 +333,7 @@ add_signed_attribute (ksba_cms_t cms, const char *attrstr)
   if (!ascii_strcasecmp (fields[1], "u"))
     {
       err = 0;
-      goto leave; /* Skip unsigned attruibutes.  */
+      goto leave; /* Skip unsigned attributes.  */
     }
   if (ascii_strcasecmp (fields[1], "s"))
     {