Merge #11495: [trivial] Make namespace explicit for is_regular_file

f4c4e38 [trivial] Make namespace explicit for is_regular_file (John Newbery)

Pull request description:

  is_regular_file resolves using argument dependent lookup. Make the
  namespace explicit so it's obvious where the function is defined.

  For those not familiar with argument dependent lookups:

  - http://en.cppreference.com/w/cpp/language/adl
  - https://en.wikipedia.org/wiki/Argument-dependent_name_lookup

  Thanks to C++ guru @ryanofsky for pointing this out to me.

Tree-SHA512: 919f1818081a8f90c5751181f87e13b06d90f8aec0ab873100434e55c85cca6e0e288ecc7f135e19e9b5dba7952e96b6393864b7840e20b69dd40e92a157928b

src/init.cpp

@@ -588,7 +588,7 @@ void CleanupBlockRevFiles()
     LogPrintf("Removing unusable blk?????.dat and rev?????.dat files for -reindex with -prune\n");
     fs::path blocksdir = GetDataDir() / "blocks";
     for (fs::directory_iterator it(blocksdir); it != fs::directory_iterator(); it++) {
-        if (is_regular_file(*it) &&
+        if (fs::is_regular_file(*it) &&
             it->path().filename().string().length() == 12 &&
             it->path().filename().string().substr(8,4) == ".dat")
         {