[refactoring] remove unused imports in the compiler and in some stdlib modules

lib/pure/collections/intsets.nim

@@ -20,7 +20,7 @@
 
 
 import
-  hashes, math
+  hashes
 
 type
   BitScalar = uint

lib/pure/concurrency/cpuinfo.nim

@@ -11,10 +11,8 @@
 
 include "system/inclrtl"
 
-import strutils, os
-
 when not defined(windows):
-  import posix
+  import strutils, posix, os
 
 when defined(linux):
   import linux

lib/pure/hashes.nim

@@ -44,10 +44,6 @@
 ## * `std/sha1 module <sha1.html>`_ for a sha1 encoder and decoder
 ## * `tables module <tables.html>`_ for hash tables
 
-
-import
-  strutils
-
 type
   Hash* = int  ## A hash value. Hash tables using these values should
                ## always have a size of a power of two and can use the ``and``

lib/pure/json.nim

@@ -142,8 +142,8 @@ runnableExamples:
   doAssert $(%* Foo()) == """{"a1":0,"a2":0,"a0":0,"a3":0,"a4":0}"""
 
 import
-  hashes, tables, strutils, lexbase, streams, unicode, macros, parsejson,
-  typetraits, options
+  hashes, tables, strutils, lexbase, streams, macros, parsejson,
+  options
 
 export
   tables.`$`

lib/pure/os.nim

@@ -1849,7 +1849,7 @@ proc expandFilename*(filename: string): string {.rtl, extern: "nos$1",
           break
     # getFullPathName doesn't do case corrections, so we have to use this convoluted
     # way of retrieving the true filename
-    for x in walkFiles(result.string):
+    for x in walkFiles(result):
       result = x
     if not existsFile(result) and not existsDir(result):
       raise newException(OSError, "file '" & result & "' does not exist")

lib/pure/terminal.nim

@@ -19,7 +19,7 @@
 import macros
 import strformat
 from strutils import toLowerAscii, `%`
-import colors, tables
+import colors
 
 when defined(windows):
   import winlean