Nimscript: added support for 'patchFile'

tests/newconfig/mymath.nim

@@ -0,0 +1,4 @@
+
+
+proc ln*(x: float): float =
+  return 0.5

tests/newconfig/tfoo.nim

@@ -1,10 +1,12 @@
 discard """
   cmd: "nim default $file"
-  output: '''hello world!'''
+  output: '''hello world! 0.5'''
   msg: '''[NimScript] exec: gcc -v'''
 """
 
 when not defined(definedefine):
   {.fatal: "wrong nim script configuration".}
 
-echo "hello world!"
+import math
+
+echo "hello world! ", ln 2.0

tests/newconfig/tfoo.nims

@@ -11,6 +11,8 @@ import ospaths
 warning("uninit", off)
 hint("processing", off)
 
+patchFile("stdlib", "math", "mymath")
+
 task listDirs, "lists every subdirectory":
   for x in listDirs("."):
     echo "DIR ", x