Rewrite the entire code-base

The following changes are focused upon:
- Modularity
- Doing away with globals
- No heap allocations
- Better command line interface
- Switch from Xlib to XCB
- More verbose type definitions
- Implement a single-file config by utilising X-macros

include/block.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <bits/stdint-uintn.h>
+#include <stdbool.h>
+#include <sys/types.h>
+
+#include "config.h"
+#include "util.h"
+
+typedef struct {
+    const char *const command;
+    const unsigned int interval;
+    const int signal;
+
+    int pipe[PIPE_FD_COUNT];
+    char output[MAX_BLOCK_OUTPUT_LENGTH * UTF8_MAX_BYTE_COUNT + 1];
+    pid_t fork_pid;
+} block;
+
+int block_init(block *const block);
+int block_deinit(block *const block);
+int block_execute(block *const block, const uint8_t button);
+int block_update(block *const block);
+bool block_must_run(const block *const block, const unsigned int time);