fixes --os:standalone

lib/system.nim

@@ -1889,9 +1889,11 @@ when not defined(JS): #and not defined(NimrodVM):
 
     # text file handling:
     var
-      stdin* {.importc: "stdin", noDecl.}: TFile   ## The standard input stream.
+      stdin* {.importc: "stdin", header: "<stdio.h>".}: TFile
-      stdout* {.importc: "stdout", noDecl.}: TFile ## The standard output stream.
+        ## The standard input stream.
-      stderr* {.importc: "stderr", noDecl.}: TFile
+      stdout* {.importc: "stdout", header: "<stdio.h>".}: TFile
+        ## The standard output stream.
+      stderr* {.importc: "stderr", header: "<stdio.h>".}: TFile
         ## The standard error stream.
         ##
         ## Note: In my opinion, this should not be used -- the concept of a

lib/system/ansi_c.nim

@@ -34,9 +34,9 @@ type
   C_JmpBuf {.importc: "jmp_buf", header: "<setjmp.h>".} = array[0..31, int]
 
 var
-  c_stdin {.importc: "stdin", header: "<stdio.h>".}: C_TextFileStar
+  c_stdin {.importc: "stdin", nodecl.}: C_TextFileStar
-  c_stdout {.importc: "stdout", header: "<stdio.h>".}: C_TextFileStar
+  c_stdout {.importc: "stdout", nodecl.}: C_TextFileStar
-  c_stderr {.importc: "stderr", header: "<stdio.h>".}: C_TextFileStar
+  c_stderr {.importc: "stderr", nodecl.}: C_TextFileStar
 
 # constants faked as variables:
 when not defined(SIGINT):
@@ -109,8 +109,9 @@ proc c_free(p: pointer) {.importc: "free", header: "<stdlib.h>".}
 proc c_realloc(p: pointer, newsize: int): pointer {.
   importc: "realloc", header: "<stdlib.h>".}
 
-when not defined(errno):
+when hostOS != "standalone":
-  var errno {.importc, header: "<errno.h>".}: cint ## error variable
+  when not defined(errno):
+    var errno {.importc, header: "<errno.h>".}: cint ## error variable
 proc strerror(errnum: cint): cstring {.importc, header: "<string.h>".}
 
 proc c_remove(filename: CString): cint {.

tests/manyloc/standalone/barebone.nim

@@ -1,4 +1,6 @@
 
 proc printf(frmt: cstring) {.varargs, header: "<stdio.h>", cdecl.}
 
-printf("hi %ld\n", 4777)
+var x = 0
+inc x
+printf("hi %ld\n", x+4777)