common/parse-bool.c: make parse_bool() generic

...to avoid multiple versions of a boolean-parser.

- Optionally take a default value
- Return -1 on error
- Rename get-bool.c to parse-bool.c

src/common/parse-bool.c

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <string.h>
+#include <strings.h>
+#include <wlr/util/log.h>
+#include "common/parse-bool.h"
+
+int
+parse_bool(const char *str, int default_value)
+{
+	if (!str) {
+		goto error_not_a_boolean;
+	} else if (!strcasecmp(str, "yes")) {
+		return true;
+	} else if (!strcasecmp(str, "true")) {
+		return true;
+	} else if (!strcasecmp(str, "no")) {
+		return false;
+	} else if (!strcasecmp(str, "false")) {
+		return false;
+	}
+error_not_a_boolean:
+	wlr_log(WLR_ERROR, "(%s) is not a boolean value", str);
+	return default_value;
+}
+