file: Support unicode urls on windows

Closes https://github.com/curl/curl/pull/6501

tests/FILEFORMAT.md

@@ -406,6 +406,7 @@ Features testable here are:
 - `TLS-SRP`
 - `TrackMemory`
 - `typecheck`
+- `Unicode`
 - `unittest`
 - `unix-sockets`
 - `verbose-strings`

tests/data/Makefile.inc

@@ -201,7 +201,7 @@ test1630 test1631 test1632 test1633 test1634 \
 test1650 test1651 test1652 test1653 test1654 test1655 \
 test1660 \
 \
-test1700 test1701 test1702 \
+test1700 test1701 test1702 test1703 \
 \
 test1800 test1801 \
 \

tests/data/test1703

@@ -0,0 +1,45 @@
+<testcase>
+<info>
+<keywords>
+FILE
+</keywords>
+</info>
+
+<reply>
+<data>
+foo
+   bar
+bar
+   foo
+moo
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+file
+</server>
+<features>
+Unicode
+win32
+</features>
+<name>
+basic file:// file with UTF-8 characters
+</name>
+<command option="no-include">
+file://localhost%FILE_PWD/log/%E3%83%86%E3%82%B9%E3%83%881703.txt
+</command>
+<file name="log/テスト1703.txt">
+foo
+   bar
+bar
+   foo
+moo
+</file>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+</verify>
+</testcase>

tests/runtests.pl

@@ -268,6 +268,7 @@ my $has_manual;     # set if built with built-in manual
 my $has_win32;      # set if built for Windows
 my $has_mingw;      # set if built with MinGW (as opposed to MinGW-w64)
 my $has_hyper = 0;  # set if built with Hyper
+my $has_unicode;    # set if libcurl is built with Unicode support
 
 # this version is decided by the particular nghttp2 library that is being used
 my $h2cver = "h2c";
@@ -2826,6 +2827,7 @@ sub setupfeatures {
     $feature{"threaded-resolver"} = $has_threadedres;
     $feature{"TLS-SRP"} = $has_tls_srp;
     $feature{"TrackMemory"} = $has_memory_tracking;
+    $feature{"Unicode"} = $has_unicode;
     $feature{"unittest"} = $debug_build;
     $feature{"unix-sockets"} = $has_unix;
     $feature{"win32"} = $has_win32;
@@ -3093,6 +3095,9 @@ sub checksystem {
                 # 'https-proxy' is used as "server" so consider it a protocol
                 push @protocols, 'https-proxy';
             }
+            if($feat =~ /Unicode/i) {
+                $has_unicode = 1;
+            }
         }
         #
         # Test harness currently uses a non-stunnel server in order to