Remove `rb_get_end` lookup in `allocProtection`
I made a local  [commit](https://github.com/devarajabc/box64/commit/1b00139bbf932ae958f8b8ac52e4da435bd0c696) and it passes my tests ( CI and ansibenchmark), saving one **O(log n)** tree lookup on every call.

However, I'm not sure if I missed anything, especially since the original comment says:
> **block is here or absent, no half-block handled..**
> **don't need to add precise tracking probably**

I'm unclear on what it refers to.

From my understand:

`allocProtection()` is responsible for inserting new memory mappings into `mapallmem`, mirroring what’s in `/proc/self/maps` (via `loadProtectionFromMap()`).

Currently, before inserting a new allocation, `rb_get_end` checks whether the memory range already exists. However, this introduces several issues:

1. Partial-range bug

    If addr lies inside an existing node but the new mapping extends past its end, `rb_get_end` returns true and skips the insertion—losing the “tail” of the new range.

2. High-memory reservations

    `reserveHighMem()` is called only once at startup to reserve a region above user-space . 
Since that reserved range never expands, we might skip all `allocProtection` calls for addresses within it.


3. Tree insert semantics

     `rb_set()`  skips duplicates, so the preliminary lookup might be save.

```diff
void allocProtection(uintptr_t addr, size_t size, uint32_t prot)
{
+   uintptr_t Reseved_addr = box64_is32bits?(1ULL<<32):(1ULL<<47);
+   if (addr >= Reseved_addr)
+      return;
   dynarec_log(LOG_DEBUG, "allocProtection %p:%p 0x%x\n", (void*)addr, (void*)(addr+size-1), prot);
   size = ALIGN(size);
   addr &= ~(box64_pagesize-1);
    LOCK_PROT();
-   uint32_t val;
-   uintptr_t endb; 
-   int there = rb_get_end(mapallmem, addr, &val, &endb);
    // block is here or absent, no half-block handled..
-  if(!there)
        rb_set(mapallmem, addr, addr+size, MEM_ALLOCATED);
    UNLOCK_PROT();
    // don't need to add precise tracking probably
}
```