Util/ASCII: add StringEqualsCaseASCII() overload with length

Replaces GLib's g_ascii_strncasecmp().

src/mixer/OssMixerPlugin.cxx

@@ -21,12 +21,11 @@
 #include "MixerInternal.hxx"
 #include "OutputAPI.hxx"
 #include "system/fd_util.h"
+#include "util/ASCII.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
 
-#include <glib.h>
-
 #include <assert.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -71,7 +70,7 @@ oss_find_mixer(const char *name)
 	size_t name_length = strlen(name);
 
 	for (unsigned i = 0; i < SOUND_MIXER_NRDEVICES; i++) {
-		if (g_ascii_strncasecmp(name, labels[i], name_length) == 0 &&
+		if (StringEqualsCaseASCII(name, labels[i], name_length) &&
 		    (labels[i][name_length] == 0 ||
 		     labels[i][name_length] == ' '))
 			return i;