patch 9.0.1208: code is indented more than necessary

Problem:    Code is indented more than necessary.
Solution:   Use an early return where it makes sense. (Yegappan Lakshmanan,
            closes #11819)
diff --git a/src/os_mac_conv.c b/src/os_mac_conv.c
index a699ce0..18e5547 100644
--- a/src/os_mac_conv.c
+++ b/src/os_mac_conv.c
@@ -568,28 +568,28 @@
     void
 mac_lang_init(void)
 {
-    if (mch_getenv((char_u *)"LANG") == NULL)
-    {
-	char	buf[50];
+    if (mch_getenv((char_u *)"LANG") != NULL)
+	return;
 
-	// $LANG is not set, either because it was unset or Vim was started
-	// from the Dock.  Query the system locale.
-	if (LocaleRefGetPartString(NULL,
-		    kLocaleLanguageMask | kLocaleLanguageVariantMask |
-		    kLocaleRegionMask | kLocaleRegionVariantMask,
-		    sizeof(buf) - 10, buf) == noErr && *buf)
-	{
-	    if (strcasestr(buf, "utf-8") == NULL)
-		strcat(buf, ".UTF-8");
-	    vim_setenv((char_u *)"LANG", (char_u *)buf);
+    char	buf[50];
+
+    // $LANG is not set, either because it was unset or Vim was started
+    // from the Dock.  Query the system locale.
+    if (LocaleRefGetPartString(NULL,
+		kLocaleLanguageMask | kLocaleLanguageVariantMask |
+		kLocaleRegionMask | kLocaleRegionVariantMask,
+		sizeof(buf) - 10, buf) == noErr && *buf)
+    {
+	if (strcasestr(buf, "utf-8") == NULL)
+	    strcat(buf, ".UTF-8");
+	vim_setenv((char_u *)"LANG", (char_u *)buf);
 #   ifdef HAVE_LOCALE_H
-	    setlocale(LC_ALL, "");
+	setlocale(LC_ALL, "");
 #   endif
 #   if defined(LC_NUMERIC)
-	    // Make sure strtod() uses a decimal point, not a comma.
-	    setlocale(LC_NUMERIC, "C");
+	// Make sure strtod() uses a decimal point, not a comma.
+	setlocale(LC_NUMERIC, "C");
 #   endif
-	}
     }
 }
 #endif // MACOS_CONVERT