avutil/log: drop support for NO_COLOR environment variable

Deprecated for more than 9 years now.
Signed-off-by: Marton Balint <cus@passwd.hu>

doc/fftools-common-opts.texi

@@ -236,10 +236,8 @@ ffmpeg [...] -loglevel +repeat
 By default the program logs to stderr. If coloring is supported by the
 terminal, colors are used to mark errors and warnings. Log coloring
 can be disabled setting the environment variable
-@env{AV_LOG_FORCE_NOCOLOR} or @env{NO_COLOR}, or can be forced setting
+@env{AV_LOG_FORCE_NOCOLOR}, or can be forced setting
 the environment variable @env{AV_LOG_FORCE_COLOR}.
-The use of the environment variable @env{NO_COLOR} is deprecated and
-will be dropped in a future FFmpeg version.
 
 @item -report
 Dump full command line and log output to a file named

libavutil/log.c

@@ -125,8 +125,7 @@ static void check_color_terminal(void)
 #if defined(_WIN32) && HAVE_SETCONSOLETEXTATTRIBUTE && HAVE_GETSTDHANDLE
     CONSOLE_SCREEN_BUFFER_INFO con_info;
     con = GetStdHandle(STD_ERROR_HANDLE);
-    use_color = (con != INVALID_HANDLE_VALUE) && !getenv("NO_COLOR") &&
-                !getenv("AV_LOG_FORCE_NOCOLOR");
+    use_color = (con != INVALID_HANDLE_VALUE) && !getenv("AV_LOG_FORCE_NOCOLOR");
     if (use_color) {
         GetConsoleScreenBufferInfo(con, &con_info);
         attr_orig  = con_info.wAttributes;
@@ -134,14 +133,13 @@ static void check_color_terminal(void)
     }
 #elif HAVE_ISATTY
     char *term = getenv("TERM");
-    use_color = !getenv("NO_COLOR") && !getenv("AV_LOG_FORCE_NOCOLOR") &&
+    use_color = !getenv("AV_LOG_FORCE_NOCOLOR") &&
                 (getenv("TERM") && isatty(2) || getenv("AV_LOG_FORCE_COLOR"));
     if (   getenv("AV_LOG_FORCE_256COLOR")
         || (term && strstr(term, "256color")))
         use_color *= 256;
 #else
-    use_color = getenv("AV_LOG_FORCE_COLOR") && !getenv("NO_COLOR") &&
-               !getenv("AV_LOG_FORCE_NOCOLOR");
+    use_color = getenv("AV_LOG_FORCE_COLOR") && !getenv("AV_LOG_FORCE_NOCOLOR");
 #endif
 }