Follow the Linux kernel's lead on "fallthrough"

The pseudo keyword 'fallthrough' is defined such that case statement
blocks must end with any of these keywords:
 * break;
 * fallthrough;
 * continue;
 * goto <label>;
 * return [expression];
 *
 *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes

The macro is defined either as

  __attribute__((__fallthrough__))

or as

  do {} while (0)  /* fallthrough */

not including the semicolon.

This change implements the Linux kernel style and updates several locations
where "/*fallthrough*/ and /* FALLTHROUGH */ were not previously replaced.

Externally imported code such as libedit, libtommath and sqlite are
restored to their unaltered state.

Change-Id: I69db8167b0d5884f55d96d72de3059a0235a1ba3

lib/ntlm/digest.c

@@ -471,8 +471,7 @@ heim_digest_generate_challenge(heim_digest_t context)
 	    break;
 	case HEIM_DIGEST_TYPE_AUTO:
 	    context->type = HEIM_DIGEST_TYPE_RFC2831;
-	    /* FALLTHROUGH */
-            fallthrough
+            fallthrough;
 	case HEIM_DIGEST_TYPE_RFC2831:
 	    asprintf(&challenge, "realm=\"%s\",nonce=\"%s\",qop=\"%s\",algorithm=md5-sess,charset=utf-8,maxbuf=%s",
 		     context->serverRealm, context->serverNonce, context->serverQOP, context->serverMaxbuf);