No out-of-line calls are generated on X86 for callees in between inlined and bailout

Created by: fhahn

While adding tests for opt_cleancall=1 (#2395) I noticed that no no out-of-line calls are generated on X86.

On X86 the following condition must be true to generate out-of-line calls:

cci->num_simd_skip == 0 /* save all xmms */ && 
cci->num_regs_skip == 0 /* save all regs */ && 
!cci->skip_save_flags

But it looks like XSP is always considered callee saved, so there is always at least 1 register that can be skipped.

#2395 contains more information in the comments