Ensure syscall functions are consistently prefixed with "NaClSys"

src/trusted/service_runtime/arch/x86_64/nacl_text_pad_test.S

 /*
  * Copyright 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "native_client/src/trusted/service_runtime/include/bits/nacl_syscalls.h"
 #include "native_client/src/trusted/service_runtime/nacl_config.h"
 
 #if defined(PNACL_AS)
 #define call naclcall
@@ skipping 110 matching lines @@
 
         leaq end_of_text, %rsi
         movq $1, %rdi
         call write_num_16
 
         movq $'\n', %rsi
         movq $1, %rdi
         call write_char
 
         movq $0, %rdi
-        movq $NACL_SYSCALL_ADDR(NACL_sys_sysbrk), %r10
+        movq $NACL_SYSCALL_ADDR(NACL_sys_brk), %r10
         naclcall %r10d,%r15
 
         xorq %r12, %r12  /* r12 holds our eventual exit status */
         cmpl $EXPECTED_BREAK, %eax
         je brk_sane
         movq $1, %r12
 brk_sane:
 
         movq %rax, %rsi
         movq $1, %rdi
@@ skipping 57 matching lines @@
 #else
         .skip TEXT_EXTEND - (. - start_of_text), 0xf4
 #endif
 end_of_text:
 
 #if defined(EXPECTED_RODATA)
         .section .rodata
 ro_str: .ascii "Hello world\n"
         /*      123456789012 */
 #endif