sys/posix: impl rest of linux, impl some of Windows

core/sys/posix/string.odin

@@ -1,3 +1,4 @@
+#+build linux, darwin, netbsd, openbsd, freebsd
 package posix
 
 import "core:c"
@@ -13,16 +14,6 @@ when ODIN_OS == .Darwin {
 // NOTE: most of the symbols in this header are not useful in Odin and have been left out.
 
 foreign lib {
-	/*
-	Map the error number to a locale-dependent error message string.
-
-	Returns: a string that may be invalidated by subsequent calls
-
-	[[ More; https://pubs.opengroup.org/onlinepubs/9699919799/functions/strerror.html ]]
-	*/
-	@(link_name="strerror")
-	_strerror :: proc(errnum: Errno) -> cstring ---
-
 	/*
 	Map the error number to a locale-dependent error message string and put it in the buffer.
 
@@ -41,7 +32,3 @@ foreign lib {
 	*/
 	strsignal :: proc(sig: Signal) -> cstring ---
 }
-
-strerror :: #force_inline proc "contextless" (errnum: Maybe(Errno) = nil) -> cstring {
-	return _strerror(errnum.? or_else errno())
-}