add test

Author: krux02

tests/float/tfloat8.nim

@@ -0,0 +1,19 @@
+discard """
+disabled: windows
+"""
+
+{.passL: "-lm".} # not sure how to do this on windows
+
+import strutils
+
+proc nextafter(a,b: float64): float64 {.importc: "nextafter", header: "<math.h>".}
+
+var myFloat = 2.5
+
+for i in 0 .. 100:
+  let newFloat = nextafter(myFloat, Inf)
+  let oldStr = $myFloat
+  let newStr = $newFloat
+  doAssert parseFloat(newStr) == newFloat
+  doAssert oldStr != newStr
+  myFloat = newFloat