feat: add string manipulation functions derived from musl libc

This commit introduces a variety of string manipulation functions, including:
- `memmem`: Searches for a substring in a memory area.
- `memmove`: Safely copies memory areas, handling overlaps.
- `mempcpy`: Copies memory and returns a pointer to the end of the destination.
- `memrchr`: Finds the last occurrence of a character in a memory area.
- `memset`: Fills a memory area with a specified value.
- `rindex`: Returns the last occurrence of a character in a string.
- `stpcpy` and `stpncpy`: Copies strings and returns a pointer to the end.
- `strcat`, `strchr`, `strcspn`, `strlcat`, `strlcpy`, `strlen`, `strncat`, `strncmp`, `strncpy`, `strnlen`, `strpbrk`, `strrchr`, `strstr`, `strtok`, and `strtok_r`: Various string manipulation functions for concatenation, searching, and tokenization.

Assembly implementations for `memcpy`, `memmove`, and `memset` are also included for optimized performance on x86_64 architectures.

1 files changed, 15 insertions, 0 deletions

diff --git a/na/include/libc-shim/bits/alltypes.h b/na/include/libc-shim/bits/alltypes.h
new file mode 100644
index 0000000..cf21a5e
--- /dev/null
+++ b/na/include/libc-shim/bits/alltypes.h
@@ -0,0 +1,15 @@
+/* Shim: provide types musl string functions need */
+#ifndef _BITS_ALLTYPES_H
+#define _BITS_ALLTYPES_H
+
+#ifndef __cplusplus
+typedef unsigned long size_t;
+#endif
+
+typedef long ssize_t;
+typedef unsigned long uintptr_t;
+
+/* locale_t stub — unused in kernel, but declared by some headers */
+typedef void *locale_t;
+
+#endif