Provide custom std #136
Description
Some applications are written against std but don't require too many features. The most popular ones are IO-related, thread-locals should be also trivial (and useful), anything doing synchronization (there are no threads; attempts to create threads should not compile).
Potentially also allow virtual filesystem. TCP would be nice but likely controversial.
Unfortunately, I think this requires either pinning the compiler version or provide std for every supported version.