Windows: accept backslashes in file names

Without this patch, a warning gets printed for any .yang files that are
read using native path names:

 libyang[1]: File name "D:\a\oopt-gnpy-libyang\oopt-gnpy-libyang\tests\yang\ietf-network@2018-02-26.yang" does not match module name "ietf-network".

src/tree_schema_common.c

@@ -2599,6 +2599,13 @@ ly_check_module_filename(const struct ly_ctx *ctx, const char *name, const char
 
     /* check that name and revision match filename */
     basename = strrchr(filename, '/');
+#ifdef _WIN32
+    const char *backslash = strrchr(filename, '\\');
+
+    if (!basename || (basename && backslash && (backslash > basename))) {
+        basename = backslash;
+    }
+#endif
     if (!basename) {
         basename = filename;
     } else {

tools/lint/common.c

@@ -54,6 +54,7 @@ parse_schema_path(const char *path, char **dir, char **module)
 
     /* split the path to dirname and basename for further work */
     *dir = strdup(path);
+    /* FIXME: this is broken on Windows */
     *module = strrchr(*dir, '/');
     if (!(*module)) {
         *module = *dir;