Multiple changes required to implement the wasmer terminal on the browser

- Split functionality out of WasiEnv so that it can support multi-threading
- Added methods to the VFS File Trait that supporting polling
- Implemented basic time functionality for WASI
- Incorported a yield callback for when WASI processes idle
- Improved the error handling on WASI IO calls
- Reduce the verbose logging on some critical WASI calls (write/read)
- Implemented the missing poll functionality for WASI processes
- Moved the syspoll functionality behind a feature flag to default to WASI method
- Refactored the thread sleeping functionality for WASI processes
- Fixed the files system benchmark which was not compiling
- Modified the file system trait so that it is SYNC and thus can handle multiple threads
- Removed the large mutex around filesystem state and implemented granular locks instead
  (this is needed to fix a deadlock scenario on the terminal)
- Split the inodes object apart from the state to fix the deadlock scenario.
- Few minor fixes to some warnings when not using certain features
- Sleeping will now call a callback that can be used by the runtime operator when
  a WASI thread goes to sleep (for instance to do other work)
- Fixed a bug where paths that exist on the real file system are leaking into VFS
- Timing functions now properly return a time precision on WASI
- Some improved macros for error handling within syscalls (wasi_try_ok!)
- Refactored the remove_directory WASI function which was not working properly
- Refactored the unlink WASI function which was not working properly
- Refactored the poll WASI function which was not working properly
- Updates some of the tests to make them compile again
- Rewrote the OutputCapturer so that it does leak into the internals

lib/c-api/src/wasm_c_api/wasi/mod.rs

@@ -19,7 +19,7 @@ use std::os::raw::c_char;
 use std::slice;
 use wasmer_api::{Exportable, Extern};
 use wasmer_wasi::{
-    generate_import_object_from_env, get_wasi_version, WasiEnv, WasiFile, WasiState,
+    generate_import_object_from_thread, get_wasi_version, WasiEnv, WasiFile, WasiState,
     WasiStateBuilder, WasiVersion,
 };
 
@@ -229,7 +229,8 @@ pub unsafe extern "C" fn wasi_env_read_stderr(
 ) -> isize {
     let inner_buffer = slice::from_raw_parts_mut(buffer as *mut _, buffer_len as usize);
     let mut state = env.inner.state();
-    let stderr = if let Ok(stderr) = state.fs.stderr_mut() {
+    let inodes = state.inodes.write().unwrap();
+    let stderr = if let Ok(stderr) = inodes.stderr_mut(&state.fs.fd_map) {
         if let Some(stderr) = stderr.as_mut() {
             stderr
         } else {
@@ -345,7 +346,8 @@ fn wasi_get_imports_inner(
     let version = c_try!(get_wasi_version(&module.inner, false)
         .ok_or("could not detect a WASI version on the given module"));
 
-    let import_object = generate_import_object_from_env(store, wasi_env.inner.clone(), version);
+    let mut thread = wasi_env.inner.new_thread();
+    let import_object = generate_import_object_from_thread(store, thread, version);
 
     imports.set_buffer(c_try!(module
         .inner