signed is not compatible with unsigned
better op_to_str()
check for always true/false unsigned comparisons
better comment for out_op why we change the type
fixes for signed vs unsigned code gen (see extended commit msg)

signed vs unsigned comparison results in a bool. We were reading the
->is_signed from this instead of storing the comparison argument's
signed/unsigned property. This commit fixes this.
proper signed/unsigned conversion rules
casts with signed/unsigned
Added signed tests
Initial data_store refactor for expr_string
Partial removal of data_store
expr_string tests
data_store, memcpy() and expr.bits refactor
Working new string generation
Fixed infinite loop (prev commit) for type_ref_is_signed
'>' works with unsigned zero
fixed signed/unsigned type checking
added __builtin_is_signed
signed tests
Merge branch 'experimental/signed_unsigned' into experimental/base

Conflicts:
	src/cc1/ops/__builtin.c

("val" union renamed to "bits")
Fixed negative and none plus/minus op applied to global address (in init)