Made trampolines less likely to interfere with level design:

Made trampolines less likely to interfere with level design:
Portables can (again) only be grabbed from the side, so taking a trampoline and using it at the same time is no longer possible.
Tux can no longer run while carrying a portable, so a gap that can only be jumped when running cannot be crossed with a trampoline.
Reduced level C1's difficulty and replaced level_flip with trampoline.

SVN-Revision: 4021