patch 8.0.1213: setting 'mzschemedll' has no effect

Problem:    Setting 'mzschemedll' has no effect.
Solution:   Move loading .vimrc to before call to mzscheme_main().
diff --git a/src/main.c b/src/main.c
index fd96f41..3db8efb 100644
--- a/src/main.c
+++ b/src/main.c
@@ -403,12 +403,26 @@
     debug_break_level = params.use_debug_break_level;
 #endif
 
+    /* Reset 'loadplugins' for "-u NONE" before "--cmd" arguments.
+     * Allows for setting 'loadplugins' there. */
+    if (params.use_vimrc != NULL
+	    && (STRCMP(params.use_vimrc, "NONE") == 0
+		|| STRCMP(params.use_vimrc, "DEFAULTS") == 0))
+	p_lpl = FALSE;
+
+    /* Execute --cmd arguments. */
+    exe_pre_commands(&params);
+
+    /* Source startup scripts. */
+    source_startup_scripts(&params);
+
 #ifdef FEAT_MZSCHEME
     /*
      * Newer version of MzScheme (Racket) require earlier (trampolined)
      * initialisation via scheme_main_setup.
      * Implement this by initialising it as early as possible
      * and splitting off remaining Vim main into vim_main2().
+     * Do source startup scripts, so that 'mzschemedll' can be set.
      */
     return mzscheme_main();
 #else
@@ -427,19 +441,6 @@
 vim_main2(void)
 {
 #ifndef NO_VIM_MAIN
-    /* Reset 'loadplugins' for "-u NONE" before "--cmd" arguments.
-     * Allows for setting 'loadplugins' there. */
-    if (params.use_vimrc != NULL
-	    && (STRCMP(params.use_vimrc, "NONE") == 0
-		|| STRCMP(params.use_vimrc, "DEFAULTS") == 0))
-	p_lpl = FALSE;
-
-    /* Execute --cmd arguments. */
-    exe_pre_commands(&params);
-
-    /* Source startup scripts. */
-    source_startup_scripts(&params);
-
 #ifdef FEAT_EVAL
     /*
      * Read all the plugin files.