fix
hook up fixbyvalattributes
introduce the attribute no_softboundcets for functions on the C level

to decide in source code whether softbound is enabled (-fsoftbound), we define:
(else 0)

on the LLVM level, we insert the Attribute::SoftboundCETS in every function definition which does not have the attribute no_softboundcets

In the SoftBoundCETS pass, we use that Attribute to decide whether to insert the softbound runtime checks
Further refactorings, especially:
 do not rename functions
 add SoftboundCETS attribute to pseudo_main
remove uneeded headers
remove uneeded wrappers
introduce two attributes:
 no_softboundCETS_calling_convention to mark functions which do not use the SB CC
 no_softboundCETS_instrument_body to mark functions whose body should not be instrumented
move runtime; integrate startup into _start; provide NO_SB_CC / NO_SB_IB macros in sys/cdefs; runtime.h in include
skip dtors
add testcase
__softbound_mmap
__softbound_mmap fix
include libc_private
add all symbols of __softboundcets to map