Kernel: Remove strncpy() and strrchr()

These are not called anywhere in the kernel anyway.

Kernel/StdLib.cpp

@@ -153,16 +153,6 @@ char* strcpy(char* dest, const char* src)
     return dest;
 }
 
-char* strncpy(char* dest, const char* src, size_t n)
-{
-    size_t i;
-    for (i = 0; i < n && src[i] != '\0'; ++i)
-        dest[i] = src[i];
-    for (; i < n; ++i)
-        dest[i] = '\0';
-    return dest;
-}
-
 void memset_user(void* dest_ptr, int c, size_t n)
 {
     ASSERT(Kernel::is_user_range(VirtualAddress(dest_ptr), n));
@@ -196,17 +186,6 @@ void* memset(void* dest_ptr, int c, size_t n)
     return dest_ptr;
 }
 
-char* strrchr(const char* str, int ch)
-{
-    char* last = nullptr;
-    char c;
-    for (; (c = *str); ++str) {
-        if (c == ch)
-            last = const_cast<char*>(str);
-    }
-    return last;
-}
-
 size_t strlen(const char* str)
 {
     size_t len = 0;

Kernel/StdLib.h

@@ -43,7 +43,6 @@ void memset_user(void*, int, size_t);
 
 void* memcpy(void*, const void*, size_t);
 char* strcpy(char*, const char*);
-char* strncpy(char*, const char*, size_t);
 int strncmp(const char* s1, const char* s2, size_t n);
 char* strstr(const char* haystack, const char* needle);
 int strcmp(char const*, const char*);
@@ -51,7 +50,6 @@ size_t strlen(const char*);
 size_t strnlen(const char*, size_t);
 void* memset(void*, int, size_t);
 int memcmp(const void*, const void*, size_t);
-char* strrchr(const char* str, int ch);
 void* memmove(void* dest, const void* src, size_t n);
 const void* memmem(const void* haystack, size_t, const void* needle, size_t);