Speed up linker by 10% (#1130)

...using one weird trick.

Cecil uses file I/O to read assemblies, but for our use cases this means we're spending a ton of time context switching between kernel mode and user mode.

Memory mapped I/O is more efficient for these access patterns.

The change is bigger than I would want it to be because:
* Loading assemblies from disk is not centralized (and in fact there are more extensibility pointer that encourage everyone to do their own loading)
* Cecil violates OOP principles by giving certain kinds of streams preferential treatment (`ModuleDefinition.FileName` is useless if the assembly wasn't opened with the blessed stream kind and Cecil doesn't have a way to provide it through other means).

0 files changed, 0 insertions, 0 deletions