restore use of .type in asm, but use modern @function (vs %function)

this seems to be necessary to make the linker accept the functions in
a shared library (perhaps to generate PLT entries?)

strictly speaking libc-internal asm should not need it. i might clean
that up later.

remove all .size and .type directives for functions from the asm

these are useless and have caused problems for users trying to build
with non-gnu tools like tcc's assembler.

modernize coding style in sjlj asm

initial check-in, version 0.5.0