i386: Remove syscall assembly codes with 6 arguments

i386: Remove syscall assembly codes with 6 arguments

This patch removes i386 assembly implementation for mmap, mmap64,
semtimeop now that i386 have 6 argument syscall support from C code
and GCC 5 can inline syscalls with 6 arguments.  We also compile mmap.c,
mmap64.c and semtimedop.c with -fomit-frame-pointer since %ebp may be
used to pass the 6th argument to syscall.

Fo sysdeps/unix/sysv/linux/i386/mmap.c, with -O2 -march=i686
-mtune=generic, GCC 5.2 now generates:

<__mmap>:
   0:	sub    $0x10,%esp
   3:	mov    0x28(%esp),%eax
   7:	mov    %ebx,(%esp)
   a:	mov    0x18(%esp),%ecx
   e:	mov    %esi,0x4(%esp)
  12:	mov    0x14(%esp),%ebx
  16:	mov    %edi,0x8(%esp)
  1a:	mov    0x1c(%esp),%edx
  1e:	test   $0xfff,%eax
  23:	mov    0x20(%esp),%esi
  27:	mov    %ebp,0xc(%esp)
  2b:	mov    0x24(%esp),%edi
  2f:	jne    60 <__mmap+0x60>
  31:	shr    $0xc,%eax
  34:	mov    %eax,%ebp
  36:	mov    $0xc0,%eax
  3b:	call   *%gs:0x10
  42:	cmp    $0xfffff000,%eax
  47:	ja     65 <__mmap+0x65>
  49:	mov    (%esp),%ebx
  4c:	mov    0x4(%esp),%esi
  50:	mov    0x8(%esp),%edi
  54:	mov    0xc(%esp),%ebp
  58:	add    $0x10,%esp
  5b:	ret
  5c:	lea    0x0(%esi,%eiz,1),%esi
  60:	mov    $0xffffffea,%eax
  65:	mov    (%esp),%ebx
  68:	mov    0x4(%esp),%esi
  6c:	mov    0x8(%esp),%edi
  70:	mov    0xc(%esp),%ebp
  74:	add    $0x10,%esp
  77:	jmp    78 <__mmap+0x78>

vs sysdeps/unix/sysv/linux/i386/mmap.S:

<__mmap>:
   0:	push   %ebp
   1:	push   %ebx
   2:	push   %esi
   3:	push   %edi
   4:	mov    0x14(%esp),%ebx
   8:	mov    0x18(%esp),%ecx
   c:	mov    0x1c(%esp),%edx
  10:	mov    0x20(%esp),%esi
  14:	mov    0x24(%esp),%edi
  18:	mov    0x28(%esp),%ebp
  1c:	test   $0xfff,%ebp
  22:	mov    $0xffffffea,%eax
  27:	jne    38 <__mmap+0x38>
  29:	shr    $0xc,%ebp
  2c:	mov    $0xc0,%eax
  31:	call   *%gs:0x10
  38:	pop    %edi
  39:	pop    %esi
  3a:	pop    %ebx
  3b:	pop    %ebp
  3c:	cmp    $0xfffff000,%eax
  41:	ja     44 <__mmap+0x44>
  43:	ret
  44:	call   45 <__mmap+0x45>	45: R_386_PC32	__x86.get_pc_thunk.cx
  49:	add    $0x2,%ecx	4b: R_386_GOTPC	_GLOBAL_OFFSET_TABLE_
  4f:	mov    0x0(%ecx),%ecx	51: R_386_TLS_GOTIE	__libc_errno
  55:	neg    %eax
  57:	mov    %eax,%gs:(%ecx)
  5a:	or     $0xffffffff,%eax
  5d:	ret

The C version has:

   3:	mov    0x28(%esp),%eax
...
  1e:	test   $0xfff,%eax
...
  31:	sar    $0xc,%eax
  34:	mov    %eax,%ebp

is due to missing $ebx register constraint for inline asm.  We have
to use "r" constraint with

register unsigned int _a6 asm ("ebp") = (unsigned int) (arg6);

and compiler chose %eax for offset (arg6) in

  if (offset & (MMAP_PAGE_UNIT - 1))

	* sysdeps/unix/sysv/linux/i386/Makefile (CFLAGS-epoll_pwait.c):
	Add -fomit-frame-pointer.
	(CFLAGS-mmap.c): Likewise.
	(CFLAGS-mmap64.c): Likewise.
	(CFLAGS-semtimedop.c): Likewise.
	* sysdeps/unix/sysv/linux/i386/mmap.c: New file.
	* sysdeps/unix/sysv/linux/i386/mmap.S: Remove file.
	* sysdeps/unix/sysv/linux/i386/mmap64.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/semtimedop.S: Likewise.