Implement errno in LibC.

This also meant I had to implement BSS (SHT_NOBITS) sections in ELFLoader.
I also added an strerror() so we can print out what the errors are.

LibC/errno.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#define EPERM      1    // Operation not permitted
+#define ENOENT     2    // No such file or directory
+#define ESRCH      3    // No such process
+#define EINTR      4    // Interrupted system call
+#define EIO        5    // I/O error
+#define ENXIO      6    // No such device or address
+#define E2BIG      7    // Argument list too long
+#define ENOEXEC    8    // Exec format error
+#define EBADF      9    // Bad file number
+#define ECHILD    10    // No child processes
+#define EAGAIN    11    // Try again
+#define ENOMEM    12    // Out of memory
+#define EACCES    13    // Permission denied
+#define EFAULT    14    // Bad address
+#define ENOTBLK   15    // Block device required
+#define EBUSY     16    // Device or resource busy
+#define EEXIST    17    // File exists
+#define EXDEV     18    // Cross-device link
+#define ENODEV    19    // No such device
+#define ENOTDIR   20    // Not a directory
+#define EISDIR    21    // Is a directory
+#define EINVAL    22    // Invalid argument
+#define ENFILE    23    // File table overflow
+#define EMFILE    24    // Too many open files
+#define ENOTTY    25    // Not a typewriter
+#define ETXTBSY   26    // Text file busy
+#define EFBIG     27    // File too large
+#define ENOSPC    28    // No space left on device
+#define ESPIPE    29    // Illegal seek
+#define EROFS     30    // Read-only file system
+#define EMLINK    31    // Too many links
+#define EPIPE     32    // Broken pipe
+#define EDOM      33    // Math argument out of domain of func
+#define ERANGE    34    // Math result not representable
+
+#define EOVERFLOW 75    // Value too large for defined data type
+
+
+#define __RETURN_WITH_ERRNO(rc, good_ret, bad_ret) \
+    do { \
+        if (rc < 0) { \
+            errno = -rc; \
+            return (bad_ret); \
+        } else { \
+            errno = 0; \
+            return (good_ret); \
+        } \
+    } while(0)
+
+extern "C" {
+
+extern int errno;
+
+};
+