__builtin_/__bound_: A 'stay tiny' approach to the matter

__builtin_/__bound_: A 'stay tiny' approach to the matter

tccgen.c:
- cleanup __builtin_... stuff
- merge __attribute((alias("sym"))) with __asm__("sym")
    Now one cannot have both, however for alias underscores are
    added if enabled.  For __asm__ they aren't.
tccpp.c:
- extend tcc_predefs accordingly.  Was generated with
  'cd tests/misc && tcc -run c2str.c tcc_predef.h tcc_predefs'
xxx-gen.c:
- move bcheck setjmp test to tccgen.c:gbound_args()
i386-gen.c:
- create win32 compatible stack space for big structures
tcctest.c:
- some cleanup + nicer output