Fix misspellings reported by goreportcard.com

https://goreportcard.com/report/github.com/rfjakob/gocryptfs#misspell

README.md

@@ -283,7 +283,7 @@ v1.0, 2016-07-17
   * Allows to pass mount options directly to the kernel
 * Add support for device files and suid binaries
   * Only works when running as root
-  * Must be explicitely enabled by passing "-o dev" or "-o suid" or "-o suid,dev"
+  * Must be explicitly enabled by passing "-o dev" or "-o suid" or "-o suid,dev"
 * Experimental Mac OS X support. See
   [ticket #15](https://github.com/rfjakob/gocryptfs/issues/15) for details.
 

cli_args.go

@@ -187,7 +187,7 @@ func parseCliOpts() (args argContainer) {
 			tlog.Fatal.Printf("The reverse mode and the -forcedecode option are not compatible")
 			os.Exit(exitcodes.Usage)
 		}
-		// Has the user explicitely disabled openssl using "-openssl=false/0"?
+		// Has the user explicitly disabled openssl using "-openssl=false/0"?
 		if !args.openssl && opensslAuto != "auto" {
 			tlog.Fatal.Printf("-forcedecode requires openssl, but is disabled via command-line option")
 			os.Exit(exitcodes.Usage)

internal/contentenc/content.go

@@ -108,7 +108,7 @@ func (be *ContentEnc) DecryptBlocks(ciphertext []byte, firstBlockNo uint64, file
 		pBlock, err = be.DecryptBlock(cBlock, firstBlockNo, fileID)
 		if err != nil {
 			if be.forceDecode && err == stupidgcm.ErrAuth {
-				tlog.Warn.Printf("DecryptBlocks: authentication failure in block #%d, overriden by forcedecode", firstBlockNo)
+				tlog.Warn.Printf("DecryptBlocks: authentication failure in block #%d, overridden by forcedecode", firstBlockNo)
 			} else {
 				break
 			}

internal/cryptocore/cryptocore.go

@@ -86,7 +86,7 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec
 			}
 			// stupidgcm does not create a private copy of the key, so things
 			// break when initFuseFrontend() overwrites it with zeros. Create
-			// a copy here. This is unneccessary when useHKDF == true, but
+			// a copy here. This is unnecessary when useHKDF == true, but
 			// does no harm.
 			var stupidgcmKey []byte
 			stupidgcmKey = append(stupidgcmKey, gcmKey...)