xtensa: don't expect XCHAL_* macros to be constant

xtensa: don't expect XCHAL_* macros to be constant

Get rid of the assumption that XCHAL_* macros are preprocessor
constants: don't use them in preprocessor conditionals or in static
variable initializers.

2017-06-14  Max Filippov  <jcmvbkbc@gmail.com>
bfd/
	* elf32-xtensa.c (elf_xtensa_be_plt_entry,
	elf_xtensa_le_plt_entry): Add dimension for the ABI to arrays,
	keep both windowed and call0 ABI PLT definitions.
	(elf_xtensa_create_plt_entry): Use selected ABI to choose upper
	elf_xtensa_*_plt_entry endex.
	(ELF_MAXPAGESIZE): Fix at minimal supported MMU page size.

gas/
	* config/tc-xtensa.c (density_supported, xtensa_fetch_width,
	absolute_literals_supported): Leave definitions uninitialized.
	(directive_state): Leave entries for directive_density and
	directive_absolute_literals initialized to false.
	(xg_init_global_config, xtensa_init): New functions.
	* config/tc-xtensa.h (TARGET_BYTES_BIG_ENDIAN): Define as 0.
	(HOST_SPECIAL_INIT): New definition.
	(xtensa_init): New declaration.