Improve EABI handling of string functions. Most importantly, fix
__aeabi_memset, which has the arguments in the wrong order.

branches: 1.1.50; 1.1.56;
Merge libkern + libc common files. As requested by core.

Rebase to HEAD as of a few days ago.

sync with head.

for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.

this commit was splitted into small chunks to avoid
a limitation of cvs. ("Protocol error: too many arguments")