Auto merge of #2062 - JohnTitor:wasi-wchar-t, r=JohnTitor

Declare `wchar_t` for WASI

Fixes #2045
r? `@ghost`

Author: bors

src/wasi.rs

@@ -35,6 +35,7 @@ pub type nlink_t = u64;
 pub type blksize_t = c_long;
 pub type blkcnt_t = i64;
 pub type nfds_t = c_ulong;
+pub type wchar_t = i32;
 
 pub type __wasi_rights_t = u64;