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

include/common/get-bool.h

@@ -1,15 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-#ifndef __LABWC_GET_BOOL_H
-#define __LABWC_GET_BOOL_H
-#include <stdbool.h>
-
-/**
- * get_bool - interpret string and return boolean
- * @s: string to interpret
- *
- * Note: This merely performs a case-insensitive check for 'yes' and 'true'.
- * Returns false by default.
- */
-bool get_bool(const char *s);
-
-#endif /* __LABWC_GET_BOOL_H */

include/common/parse-bool.h

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __LABWC_PARSE_BOOL_H
+#define __LABWC_PARSE_BOOL_H
+#include <stdbool.h>
+
+/**
+ * parse_bool() - Parse boolean value of string.
+ * @string: String to interpret. This check is case-insensitive.
+ * @default_value: Default value to use if string is not a recognised boolean.
+ *                 Use -1 to avoid setting a default value.
+ *
+ * Return: 0 for false; 1 for true; -1 for non-boolean
+ */
+int parse_bool(const char *str, int default_value);
+
+#endif /* __LABWC_PARSE_BOOL_H */