new VM: some progress for the FFI support

lib/system/sysio.nim

@@ -194,9 +194,9 @@ const
     # should not be translated.
 
 
-proc Open(f: var TFile, filename: string,
+proc open(f: var TFile, filename: string,
           mode: TFileMode = fmRead,
-          bufSize: int = -1): Bool =
+          bufSize: int = -1): bool =
   var p: pointer = fopen(filename, FormatOpen[mode])
   result = (p != nil)
   f = cast[TFile](p)

lib/system/widestrs.nim

@@ -101,7 +101,8 @@ proc newWideCString*(s: cstring): WideCString =
   if s.isNil: return nil
 
   when not defined(c_strlen):
-    proc c_strlen(a: CString): int {.nodecl, noSideEffect, importc: "strlen".}
+    proc c_strlen(a: cstring): int {.
+      header: "<string.h>", noSideEffect, importc: "strlen".}
 
   let L = cstrlen(s)
   result = newWideCString(s, L)