Some cleanup work

* Remove NO_C2 option
* Split configuration related functions into their own file
* Drop support for libconfig < 1.4
* Fix dependencies in Makefile

src/config.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include <libconfig.h>
+
+#include "common.h"
+
+bool parse_long(const char *, long *);
+const char *parse_matrix_readnum(const char *, double *);
+XFixed *parse_matrix(session_t *, const char *, const char **);
+XFixed *parse_conv_kern(session_t *, const char *, const char **);
+bool parse_conv_kern_lst(session_t *, const char *, XFixed **, int);
+bool parse_geometry(session_t *, const char *, geometry_t *);
+bool parse_rule_opacity(session_t *, const char *);
+
+/**
+ * Add a pattern to a condition linked list.
+ */
+bool condlst_add(session_t *, c2_lptr_t **, const char *);
+
+#ifdef CONFIG_LIBCONFIG
+FILE *
+open_config_file(char *cpath, char **path);
+
+void
+parse_cfg_condlst(session_t *ps, const config_t *pcfg, c2_lptr_t **pcondlst,
+    const char *name);
+
+void
+parse_config(session_t *ps, struct options_tmp *pcfgtmp);
+#endif