inconsistency between -O5 and -optimize-level 5 in csc

[sven]

-O5 causes the addition of C options in csc.scm, while -optimize-level 5 doesn't.
Please remove the when-statement that does this.

Some arguments for this:

1. -O5 does more than -optimize-level 5, which is undocumented

and inconsistent.

2. Furthermore, -fomit-frame-pointer might not help much if the underlying

chicken was built without this option (if I remember correctly).

3. -O3 is often not the best choice for speed, so I would recommend not to

intervene with the settings from the chicken build.

4. Finally, gcc takes the _last_ -O option if several are given, so -O3 has no

effect if "compile-options" contains any -O2 or similar.

[felix winkelmann]

Milestone 4.8.0 deleted