COMP: fix warnings on hp

Source/cmCommandArgumentLexer.cxx

@@ -1046,6 +1046,7 @@ case YY_STATE_EOF(NOESCAPES):
                         "fatal flex scanner internal error--no action found" );
         } /* end of action switch */
                 } /* end of scanning one token */
+return 0; /* this should not happend but it should silence a warning */
 } /* end of cmCommandArgument_yylex */
 
 /* yy_get_next_buffer - try to read in a new buffer

Source/cmDependsJavaLexer.cxx

@@ -1596,6 +1596,7 @@ case YY_STATE_EOF(string):
       "fatal flex scanner internal error--no action found" );
   } /* end of action switch */
     } /* end of scanning one token */
+return 0; /* this should not happen but it silences a warning*/
 } /* end of cmDependsJava_yylex */
 
 /* yy_get_next_buffer - try to read in a new buffer

Source/cmExprLexer.cxx

@@ -981,6 +981,7 @@ case YY_STATE_EOF(INITIAL):
       "fatal flex scanner internal error--no action found" );
   } /* end of action switch */
     } /* end of scanning one token */
+return 0; /* this should not happen but it silences a warning*/
 } /* end of cmExpr_yylex */
 
 /* yy_get_next_buffer - try to read in a new buffer