update clang-format to clang-format-11, fixes enum bug

[ailin-nemui]

No description provided.

[ailin-nemui]

@irssi/developers

[ailin-nemui]

Example of the bug:

diff --git a/src/fe-text/textbuffer.h b/src/fe-text/textbuffer.h
index 5f5f9a2..a8b230a 100644
--- a/src/fe-text/textbuffer.h
+++ b/src/fe-text/textbuffer.h
@@ -11,11 +11,10 @@ enum {
 	LINE_CMD_EOL=0x80,	/* line ends here */
 };
 
-enum {
-	COLORING_STRIP = 0,
-	COLORING_EXPAND = 1,
-	COLORING_UNEXPAND = 2,
-	COLORING_RAW = 3,
+enum { COLORING_STRIP = 0,
+       COLORING_EXPAND = 1,
+       COLORING_UNEXPAND = 2,
+       COLORING_RAW = 3,
 };
 
 struct _TEXT_BUFFER_FORMAT_REC;

https://github.com/irssi/irssi/runs/2107467912?check_suite_focus=true