Add exists() method in filesystem namespace as in STL's filesystem.

Author: tatsy

filesystem/path.h

@@ -431,4 +431,9 @@ inline bool create_directories(const path& p) {
 #endif
 }
 
+inline bool exists(const path& p) {
+    return p.exists();
+}
+
+
 NAMESPACE_END(filesystem)

path_demo.cpp

@@ -25,17 +25,20 @@ int main(int argc, char **argv) {
     cout << "some/path.ext:operator==() (unequal) = " << (path("some/path.ext") == path("another/path.ext")) << endl;
 
     cout << "nonexistant:exists = " << path("nonexistant").exists() << endl;
+    cout << "nonexistant:exists = " << exists(path("nonexistant")) << endl;
     cout << "nonexistant:is_file = " << path("nonexistant").is_file() << endl;
     cout << "nonexistant:is_directory = " << path("nonexistant").is_directory() << endl;
     cout << "nonexistant:filename = " << path("nonexistant").filename() << endl;
     cout << "nonexistant:extension = " << path("nonexistant").extension() << endl;
     cout << "filesystem/path.h:exists = " << path("filesystem/path.h").exists() << endl;
+    cout << "filesystem/path.h:exists = " << exists(path("filesystem/path.h")) << endl;
     cout << "filesystem/path.h:is_file = " << path("filesystem/path.h").is_file() << endl;
     cout << "filesystem/path.h:is_directory = " << path("filesystem/path.h").is_directory() << endl;
     cout << "filesystem/path.h:filename = " << path("filesystem/path.h").filename() << endl;
     cout << "filesystem/path.h:extension = " << path("filesystem/path.h").extension() << endl;
     cout << "filesystem/path.h:make_absolute = " << path("filesystem/path.h").make_absolute() << endl;
     cout << "../filesystem:exists = " << path("../filesystem").exists() << endl;
+    cout << "../filesystem:exists = " << exists(path("../filesystem")) << endl;
     cout << "../filesystem:is_file = " << path("../filesystem").is_file() << endl;
     cout << "../filesystem:is_directory = " << path("../filesystem").is_directory() << endl;
     cout << "../filesystem:extension = " << path("../filesystem").extension() << endl;