Fix some Wpedantic warnings

[yangfl]

No description provided.

[rom1v]

In scrcpy, I decided to accept compound statements. Removing some of them will not solve all warnings, I use this feature everywhere in vector and vecdeque. Tested with:

diff --git a/meson.build b/meson.build
index 847e33a10..2ed00fb51 100644
--- a/meson.build
+++ b/meson.build
@@ -3,7 +3,7 @@ project('scrcpy', 'c',
         meson_version: '>= 0.48',
         default_options: [
             'c_std=c11',
-            'warning_level=2',
+            'warning_level=3',
             'b_ndebug=if-release',
         ])
 

(there are a lot of warnings).

See my comments here:

• remove compound statements #2406 (review)
• Initial work done on making it work natively on all platforms/buildsystems  #2397 (comment)