goto-program interpreter: accurate help output

Previous help output was misleading and incomplete.

Author: tautschnig

regression/goto-interpreter/help-output/test.desc

@@ -8,10 +8,11 @@ h,q
 ^m: output memory dump$
 ^o: output goto trace$
 ^q: quit$
-^r: run until completion$
+^r: run up to entry point$
 ^s#: step a number of instructions$
 ^sa: step across a function$
 ^so: step out of a function$
+^se: step until end of program$
 ^\d+- Program End\.$
 ^EXIT=0$
 ^SIGNAL=0$

src/goto-programs/interpreter.cpp

@@ -147,10 +147,11 @@ void interpretert::command()
       << "m: output memory dump\n"
       << "o: output goto trace\n"
       << "q: quit\n"
-      << "r: run until completion\n"
+      << "r: run up to entry point\n"
       << "s#: step a number of instructions\n"
       << "sa: step across a function\n"
       << "so: step out of a function\n"
+      << "se: step until end of program\n"
       << eom;
   }
   else if(ch=='j')