Add PRIVATE flags to global symbols

simd/jcgryext-sse2-64.asm

 ;
 ; jcgryext.asm - grayscale colorspace conversion (64-bit SSE2)
 ;
 ; x86 SIMD extension for IJG JPEG library
 ; Copyright (C) 1999-2006, MIYASAKA Masaru.
 ; Copyright (C) 2011, D. R. Commander.
 ; For conditions of distribution and use, see copyright notice in jsimdext.inc
 ;
 ; This file should be assembled with NASM (Netwide Assembler),
 ; can *not* be assembled with Microsoft's MASM or any compatible
@@ skipping 19 matching lines @@
 ; r11 = JSAMPARRAY input_buf
 ; r12 = JSAMPIMAGE output_buf
 ; r13 = JDIMENSION output_row
 ; r14 = int num_rows
 
 %define wk(i)           rbp-(WK_NUM-(i))*SIZEOF_XMMWORD ; xmmword wk[WK_NUM]
 %define WK_NUM          2
 
         align   16
 
-        global  EXTN(jsimd_rgb_gray_convert_sse2)
+        global  EXTN(jsimd_rgb_gray_convert_sse2) PRIVATE
 
 EXTN(jsimd_rgb_gray_convert_sse2):
         push    rbp
         mov     rax,rsp                         ; rax = original rbp
         sub     rsp, byte 4
         and     rsp, byte (-SIZEOF_XMMWORD)     ; align to 128 bits
         mov     [rsp],rax
         mov     rbp,rsp                         ; rbp = aligned rbp
         lea     rsp, [wk(0)]
         collect_args
@@ skipping 304 matching lines @@
         pop     rbx
         uncollect_args
         mov     rsp,rbp         ; rsp <- aligned rbp
         pop     rsp             ; rsp <- original rbp
         pop     rbp
         ret
 
 ; For some reason, the OS X linker does not honor the request to align the
 ; segment unless we do this.
         align   16