Implement predefined CRCs and add libfort

include/patchelfcrc/named_crcs.h

@@ -0,0 +1,23 @@
+#ifndef _NAMED_CRCS_H_
+#define _NAMED_CRCS_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+
+struct crc_settings {
+    uint32_t polynomial;
+    uint32_t xor;
+    uint32_t start_value;
+    bool rev;
+};
+
+struct named_crc {
+    const char *name;
+    struct crc_settings settings;
+};
+
+const struct named_crc *reverse_lookup_named_crc(const struct crc_settings *settings);
+
+const struct named_crc *lookup_named_crc(const char *name);
+
+#endif /* _NAMED_CRCS_H_ */