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