nim: exit on Ctrl-D in steps 1-8

step9 and stepA had a catch handler for this but the earlier steps were
missing it.

impls/nim/step1_read_print.nim

@@ -10,5 +10,6 @@ while true:
   try:
     let line = readLineFromStdin("user> ")
     echo line.read.eval.print
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()

impls/nim/step2_eval.nim

@@ -43,5 +43,6 @@ while true:
   try:
     let line = readLineFromStdin("user> ")
     echo line.rep
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()

impls/nim/step3_env.nim

@@ -63,6 +63,7 @@ while true:
   try:
     let line = readLineFromStdin("user> ")
     echo line.rep
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()

impls/nim/step4_if_fn_do.nim

@@ -91,6 +91,7 @@ while true:
   try:
     let line = readLineFromStdin("user> ")
     echo line.rep
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()

impls/nim/step5_tco.nim

@@ -113,6 +113,7 @@ while true:
   try:
     let line = readLineFromStdin("user> ")
     echo line.rep
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()

impls/nim/step6_file.nim

@@ -123,6 +123,7 @@ while true:
     let line = readLineFromStdin("user> ")
     echo line.rep
   except Blank: discard
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()

impls/nim/step7_quote.nim

@@ -158,6 +158,7 @@ while true:
     let line = readLineFromStdin("user> ")
     echo line.rep
   except Blank: discard
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()

impls/nim/step8_macros.nim

@@ -167,6 +167,7 @@ while true:
     let line = readLineFromStdin("user> ")
     echo line.rep
   except Blank: discard
+  except IOError: quit()
   except:
     echo getCurrentExceptionMsg()
     echo getCurrentException().getStackTrace()