Add GetRedbeanVersion & rename GetVersion (#219)

- Add GetRedbeanVersion() to redbean (#97)
- Rename GetVersion to GetHttpVersion() for consistency (#97)
- Update Content-Length format to use a proper size modifier (#97, #218)

tool/net/help.txt

@@ -664,10 +664,15 @@ FUNCTIONS
            if redbean is being used as an HTTP proxy server. In the future
            this API might change to return an object instead.
 
-   GetVersion() → int
+   GetHttpVersion() → int
            Returns the request HTTP protocol version, which can be 9 for
            HTTP/0.9, 10 for HTTP/1.0, or 11 for HTTP/1.1.
 
+   GetRedbeanVersion() → int
+           Returns the Redbean version in the format 0xMMmmpp, with major (MM),
+           minor (mm), and patch (pp) versions encoded. The version value 1.4
+           would be represented as 0x010400.
+
    GetZipPaths() → array[str]
            Returns paths of all assets in the zip central directory, prefixed
            by a slash.