auto merge of #5198 : youknowone/rust/repeat-count, r=brson
Before:
````
test.rs:3:21: 3:30 error: expected constant integer for repeat count but found variable
test.rs:3 let a = ~[0, ..n]; //~ ERROR expected constant integer for repeat count but found variable
^~~~~~~~~
````
After:
````
test.rs:3:27: 3:28 error: expected constant integer for repeat count but found variable
test.rs:3 let a = ~[0, ..n]; //~ ERROR expected constant integer for repeat count but found variable
^
````