Description:
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the current "resource control" logic main/rfc1867.c implemented is not pretty enough.
it didn't take enough care of server resources when user upload "too large" file
issue 1. memory
i'd like to set post_max_size=2M or 3M etc.
but i can't, cos upload file size often exceeds this limit.
then i let it be 8M, but how if someone just post a 8m text(not file)? 8M data is get into php's memory, just 10 users can make php use 80MB memory, well there is memory_limit, but it seems only good for "php script execution memory usage", the $_POST size should be calc "alone"

issue 2. network traffic
i'd like to tune upload_max_size=8M (each file).
some user can only upload 1M pre file, we can set MAX_FILE_SIZE="<?=1024*1024?>", but then? php read up to 1M, and notice it exceeded MAX_UPLOAD_SIZE. canceling upload, starting to execute phpscript. this however waste 1Mbyte traffic, which is 8Mbits(also waste of time, _bad_ user experience)

issue 3. temp disk usage
when i set upload_max_size=1M, and post_max_upload=8M
with 8 multi uploads, each 1M, can eat up 8M disk usage(temp file).
well this isn't a teribble issue. at least, disk is always larger than memory

it's nice if we can control:
max $_POST size
	ini=?? (for "issue 1", memory usage)
	form=not needed
max Request-Content-Length
	ini=post_max_size
	form=??? (for "issue 2", cancel upload ASAP)
max size per file
	ini=upload_max_filesize
	form=MAX_FILE_SIZE
max total file size
	ini=needed?
	form=needed?
ini means: hard set in ini
form means: soft set in form,