Uses abort() instead of raising a SIGABRT signal [-Werror]

error: ‘noreturn’ function does return [-Werror]

abort() is a noreturn function while raise() is not.

And because crypt_argchk() is flagged as __attribute__(noreturn), abort()
appears to be a better condidate.

This compilation warning has probably been introduced by commit
1809f741cb.

libtomcrypt/src/misc/crypt/crypt_argchk.c

@@ -21,7 +21,7 @@ void crypt_argchk(char *v, char *s, int d)
 {
  fprintf(stderr, "LTC_ARGCHK '%s' failure on line %d of file %s\n",
          v, d, s);
- (void)raise(SIGABRT);
+ abort();
 }
 #endif