eina log bt - on by default always if unwind found

i'm tried of telling people how to turn this on. enough. on by
default. if you dont want bt's and its just some helpful log output
then just printf it or use WRN, INF and set log levels...

src/lib/eina/eina_log.c

@@ -127,7 +127,7 @@ static int _abort_level_on_critical = EINA_LOG_LEVEL_CRITICAL;
 # ifndef EINA_LOG_BACKTRACE_ENABLE
 static int _backtrace_level = -1;
 # else
-static int _backtrace_level = 1;
+static int _backtrace_level = EINA_LOG_LEVEL_ERR;
 # endif
 #endif
 

src/lib/eina/meson.build

@@ -357,6 +357,7 @@ unwind = dependency('libunwind-generic', required: false)
 if unwind.found()
    config_h.set('HAVE_UNWIND', 1)
    eina_deps += unwind
+   config_h.set('EINA_LOG_BACKTRACE_ENABLE', 1)
 endif
 
 #for the case that the iconv library is not part of libc but rather libiconv or smth. like that