PDQ-3, SAGE: Coverity Fixes

CID       Action
   1416081   changed variable answer to int
   1416082   checked returned values with ASSURE - read error means corrupted target code.
   1416088   added return
   1416109   This fallthru was intentional - duplicated code to make coverity happy
   1416111   This fallthru was intentional - duplicated code to make coverity happy
   1416116   This fallthru was intentional - duplicated code to make coverity happy
   1416117   This fallthru was intentional - duplicated code to make coverity happy
   1416124   protected against negative return
   1416142   added ASSURE, however this case won't happen since reg_intpending==true implies positive int level
   1416145   checked non-NULL, return SCPE_ARG if NULL
   1416150   since only 2 drives are supported, fdc_selected is decoded to 0 and 1 only (allowed 2 and 3 before)
   1416152   restrict to 2 drives only
   1416166   checked value with ASSURE

   1416101   typo: should have been resx
   1416106   unnecessary code removed
   1416110   this fallthru was intentional - duplicated code to make coverity happy
   1416112   this fallthru was intentional - duplicated code to make coverity happy
   1416148   change condition to check for negative value
   1416179   break was remainder from former logic - removed
   1415866   code was remainder from former unimplemented instruction trap - removed

PDQ-3/pdq3_stddev.c

@@ -264,7 +264,7 @@ t_stat con_pollsvc(UNIT *uptr) {
 
     if (isbitset(con_ctrl1, CONC1_ECHO)) { /* echo? XXX handle in telnet handler? */
       /* XXX use direct send here, not sending via con_termsvc */
-      sim_putchar_s(ch);
+      return sim_putchar_s(ch);
     }
   }
   return SCPE_OK;