Merge branch 'plain' into 7mod

Conflicts:
	configure
wip: Support ABR reconfiguration
Add autotools-style silent build rules
aarch64: optimize x264_predict_8x8c_dc_left_neon
aarch64: implement x264_pixel_sa8d_satd_16x16_neon

~20% faster than calling pixel_sa8d_16x16 and pixel_satd_16x16
separately.
aarch64: NEON asm for missing x264_zigzag_* functions

zigzag_scan_4x4_field_neon, zigzag_sub_4x4_field_neon,
zigzag_sub_4x4ac_field_neon, zigzag_sub_4x4_frame_neon,
igzag_sub_4x4ac_frame_neon more than 2 times faster

zigzag_scan_8x8_frame_neon, zigzag_scan_8x8_field_neon,
zigzag_sub_8x8_field_neon, zigzag_sub_8x8_frame_neon 4-5 times faster

zigzag_interleave_8x8_cavlc_neon 6 times faster
aarch64: implement x264_pixel_vsad_neon

35 times faster than C.
aarch64: implement x264_pixel_ssd_nv12_core_neon

13 times faster than C.
aarch64: NEON asm for 4x16 sad, satd and ssd

pixel_sad_4x16_neon: 33% faster than C
pixel_satd_4x16_neon: 5 times faster
pixel_ssd_4x16_neon:  4 times faster
aarch64: implement x264_pixel_asd8_neon

7 times faster than C.
aarch64: implement x264_sub8x16_dct_dc_neon

4 times faster than C.
aarch64: NEON asm for decimate_score

decimate_score15 and 16 are 60% faster, decimate_score64 is 4 times
faster than C.
aarch64: NEON asm for 8x16c intra prediction

Between 10% and 40% faster than C.
aarch64: NEON asm for integral init

integral_init4h_neon and integral_init8h_neon are 3-4 times faster tan
C. integral_init8v_neon is 6 times faster and integral_init4v_neon is 10
times faster.