Update: Do not force '-' into '_' in HTTP Header names, handle extra names, update...

Update: Do not force '-' into '_' in HTTP Header names, handle extra names, update comments

Apache may provide header names with '_' in place of '-', causing problems.
The standard allows for '_' and as such '_' and '-' should be mutually exclusive.

My previous behavior is to force all '-' to '_', but I believe this to be bad practice as a default behavior.
I may come back and either provide commented out code, apache-specific tests, or an example patch to apache source code.
Each approach has its problems and advantages.
I will address that issue at a later time.

Handle additional known PHP-provided HTTP headers when getallheaders() is unavailable.

Update the comments in the header processing function.