Auto merge of #2264 - sunfishcode:sunfishcode/wasi-mode-bits, r=JohnTitor

Define `S_I{R,W,X}{USR,GRP,OTH}` and `S_IS{VTX,UID,GID}` for wasi.

WASI doesn't have full permissions setting, but it's gaining some
support, so define the POSIX names that wasi-libc defines, and let
WASI libc and WASI sort out what to do with them.

Author: bors

src/wasi.rs

@@ -226,6 +226,18 @@ pub const S_IFREG: mode_t = 32768;
 pub const S_IFLNK: mode_t = 40960;
 pub const S_IFSOCK: mode_t = 49152;
 pub const S_IFMT: mode_t = 57344;
+pub const S_IXOTH: mode_t = 0x1;
+pub const S_IWOTH: mode_t = 0x2;
+pub const S_IROTH: mode_t = 0x4;
+pub const S_IXGRP: mode_t = 0x8;
+pub const S_IWGRP: mode_t = 0x10;
+pub const S_IRGRP: mode_t = 0x20;
+pub const S_IXUSR: mode_t = 0x40;
+pub const S_IWUSR: mode_t = 0x80;
+pub const S_IRUSR: mode_t = 0x100;
+pub const S_ISVTX: mode_t = 0x200;
+pub const S_ISGID: mode_t = 0x400;
+pub const S_ISUID: mode_t = 0x800;
 pub const DT_UNKNOWN: u8 = 0;
 pub const DT_BLK: u8 = 1;
 pub const DT_CHR: u8 = 2;