Auto merge of #21269 - alexcrichton:issue-6936, r=pnkfelix

This commit modifies resolve to prevent conflicts with typedef names in the same
method that conflits are prevented with enum names. This is a breaking change
due to the differing semantics in resolve, and any errors generated on behalf of
this change require that a conflicting typedef, module, or structure to be
renamed so they do not conflict.

[breaking-change]
Closes #6936

diff --cc src/librustc_trans/trans/debuginfo.rs
Simple merge

diff --cc src/librustc_typeck/astconv.rs
Simple merge

diff --cc src/librustc_typeck/collect.rs
Simple merge