Implement POSIX support for Linux for the following facilities:

- fnmatch
- grp
- langinfo
- locale

core/sys/posix/fnmatch.odin

@@ -53,6 +53,14 @@ when ODIN_OS == .Darwin || ODIN_OS == .FreeBSD || ODIN_OS == .NetBSD || ODIN_OS
 	FNM_PERIOD   :: 0x04
 	FNM_NOESCAPE :: 0x01
 
+} else when ODIN_OS == .Linux {
+
+	FNM_NOMATCH  :: 1
+
+	FNM_PATHNAME :: 0x01
+	FNM_NOESCAPE :: 0x02
+	FNM_PERIOD   :: 0x04
+
 } else {
 	#panic("posix is unimplemented for the current target")
 }