Use XCNEW gdbarch_tdep

Use XCNEW gdbarch_tdep

This patch uses XCNEW gdbarch_tdep instead of XNEW.

gdb:

2017-05-24  Yao Qi  <yao.qi@linaro.org>

	* alpha-tdep.c (alpha_gdbarch_init): Use XCNEW instead of XNEW.
	* avr-tdep.c (avr_gdbarch_init): Likewise.
	* bfin-tdep.c (bfin_gdbarch_init): Likewise.
	* cris-tdep.c (cris_gdbarch_init): Likewise.
	* ft32-tdep.c (ft32_gdbarch_init): Likewise.
	* lm32-tdep.c (lm32_gdbarch_init): Likewise.
	* m32r-tdep.c (m32r_gdbarch_init): Likewise.
	* m68hc11-tdep.c (m68hc11_gdbarch_init): Likewise.
	* mep-tdep.c (mep_gdbarch_init): Likewise.
	* microblaze-tdep.c (microblaze_gdbarch_init): Likewise.
	* mips-tdep.c (mips_gdbarch_init): Likewise.
	* mn10300-tdep.c (mn10300_gdbarch_init): Likewise.
	* moxie-tdep.c (moxie_gdbarch_init): Likewise.
	* msp430-tdep.c (msp430_gdbarch_init): Likewise.
	* sh64-tdep.c (sh64_gdbarch_init): Likewise.
	* v850-tdep.c (v850_gdbarch_init): Likewise.