Fix file paths with non-ASCII characters on windows

It was not possible to run an OpenUSD application from a directory with non-ASCII characters in it's name on windows. This is because LoadLibrary and std::ifstream were used with UTF-8-encoded file paths, while only system encoding and UTF-16 are supported. File paths are converted to UTF-16 now.

Author: mnaehrig

pxr/base/arch/library.cpp

@@ -6,6 +6,7 @@
 //
 
 #include "pxr/pxr.h"
+#include "pxr/base/arch/fileSystem.h"
 #include "pxr/base/arch/library.h"
 #include "pxr/base/arch/errno.h"
 
@@ -27,7 +28,7 @@ void* ArchLibraryOpen(const std::string &filename, int flag)
 {
 #if defined(ARCH_OS_WINDOWS)
     arch_lastLibraryError = 0;
-    if (void* result = LoadLibrary(filename.c_str())) {
+    if (void* result = LoadLibraryW(ArchWindowsUtf8ToUtf16(filename).c_str())) {
         return result;
     }
     else {

pxr/imaging/hio/glslfx.cpp

@@ -232,7 +232,11 @@ static unique_ptr<istream>
 _CreateStreamForFile(string const& filePath)
 {
     if (TfIsFile(filePath)) {
+#if defined(ARCH_OS_WINDOWS)
+        return make_unique<ifstream>(ArchWindowsUtf8ToUtf16(filePath));
+#else
         return make_unique<ifstream>(filePath);
+#endif
     }
 
     const shared_ptr<ArAsset> asset = ArGetResolver().OpenAsset(