Column offset should be 1-based instead of 0-based.

[jhasse]

Other compilers (gcc) and editors (Sublime Text, vim) start columns at 1, but the rust compiler starts at 0:

~ echo "int main() { foo }" > tmp.c
~ echo " fn main() { foo }" > tmp.rs
~ gcc tmp.c
tmp.c:1:14: error: 'foo' undeclared (first use in this function)
~ rustc tmp.rs
tmp.rs:1:13: 1:16 error: unresolved name `foo`.

I'm not sure how to fix this properly. My patch simply adds 1 whenever col is displayed, but maybe it should be changed here? https://github.com/mozilla/rust/blob/master/src/libsyntax/codemap.rs#L148

[huonw]

Dupe of #10848. (I'm not sure which is the proper fix, storing them 0-based makes indexing/slicing the strings by adding to the start-of-column offset more natural.)