add mmap_file for WIN32 and httpserver example improvements

[ManuLinares]

Can't add many features for this example of course

• hardened against directory traversal, and a bunch of other optimizations, it's still small and pretty.
• added description

<*
 This is a simple static HTTP server example. It listens on a TCP port, parses basic
 HTTP/1.1 requests, handles Keep-Alive connections, serves static files with Range
 and ETag support, applies dynamic Gzip compression, and displays directory listings.
*>

[lerno]

EXECWRITE? Why not use to_win32 and tweak it?

[lerno]

What about the size = 0 case?

[ManuLinares]

https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-mapviewoffile

[in] dwNumberOfBytesToMap

The number of bytes of a file mapping to map to the view. All bytes must be within the maximum size specified by CreateFileMapping. If this parameter is 0 (zero), the mapping extends from the specified offset to the end of the file mapping.

For zero it says is valid, and maps from the offset to the end. I could change the contract comment to reflect this?

@param size : "Number of bytes to map, will be rounded up to page size"

[ManuLinares]

for our api consistency we could, on size == 0 do aligned_alloc_size which does one win32::allocation_granularity, I don't know what's the correct path here.

[ManuLinares]

my understanding is that POSIX mmap requires the length argument be strictly greater than zero, we are rounding up now to 1 pagesize when mmap_file
maybe in posix we should also if (size == 0) return INVALID_ARGS~;

[LowByteFox]

👀 something quite useful for me

[lerno]

Thank you!