Fix generic trampoline string leak.

Generic trampolines were leaking strings because:
1. The mono_arch_create_generic_trampoline function uses mono_get_generic_trampoline_name which does strdup.
2. That string was passed into mono_tramp_info_create which did strdup again.

The fix is to free the string after passing it to mono_tramp_info_create.
Fix additional string leaks when creating tramp_info.

A recent change modified mono_tramp_info_create to duplicate the name string passed to it, but all of the references that were previously duping the name before calling were not updated at the same time. This resulted in several memory leaks. This fix removes the now extra string duplications.
Fix additional string leaks when creating tramp_info.

A recent change modified mono_tramp_info_create to duplicate the name string passed to it, but all of the references that were previously duping the name before calling were not updated at the same time. This resulted in several memory leaks. This fix removes the now extra string duplications.
Merge pull request #712 from spicypixel/hotfix/trampoline-name-leak

Fix generic trampoline string leak.