PR26457 UBSAN: som.c:1794 left shift cannot be represented

PR26457 UBSAN: som.c:1794 left shift cannot be represented

	PR 26457
	* som/aout.h (SOM_SUBSPACE_ACCESS_CONTROL_BITS_MASK): Make unsigned.
	(SOM_SUBSPACE_MEMORY_RESIDENT, SOM_SUBSPACE_DUP_COMMON)
	(SOM_SUBSPACE_IS_COMMON, SOM_SUBSPACE_IS_LOADABLE)
	(SOM_SUBSPACE_QUADRANT_MASK, SOM_SUBSPACE_INITIALLY_FROZEN)
	(SOM_SUBSPACE_IS_FIRST, SOM_SUBSPACE_CODE_ONLY)
	(SOM_SUBSPACE_SORT_KEY_MASK, SOM_SUBSPACE_REPLICATE_INIT)
	(SOM_SUBSPACE_CONTINUATION, SOM_SUBSPACE_IS_TSPECIFIC)
	(SOM_SUBSPACE_IS_COMDAT): Likewise.