util: Improve ap_cstr_casecmp() and ap_cstr_casecmpn() performances.

util: Improve ap_cstr_casecmp() and ap_cstr_casecmpn() performances.

The new versions [1] compile to a shorter/faster assembly than the previous
ones [2], no functionnal change.

[1] ap_cstr_casecmp() after this commit:
Dump of assembler code for function ap_cstr_casecmp:
   0x0000000000049fc0 <+0>:	movzbl (%rdi),%eax
   0x0000000000049fc3 <+3>:	movzbl (%rsi),%edx
   0x0000000000049fc6 <+6>:	lea    0x3d573(%rip),%r8        # 0x87540 <ucharmap>
   0x0000000000049fcd <+13>:	movzbl (%r8,%rax,1),%eax
   0x0000000000049fd2 <+18>:	movzbl (%r8,%rdx,1),%ecx
   0x0000000000049fd7 <+23>:	cmp    %ecx,%eax
   0x0000000000049fd9 <+25>:	jne    0x49ffe <ap_cstr_casecmp+62>
   0x0000000000049fdb <+27>:	xor    %edx,%edx
   0x0000000000049fdd <+29>:	jmp    0x49ffa <ap_cstr_casecmp+58>
   0x0000000000049fdf <+31>:	nop
   0x0000000000049fe0 <+32>:	add    $0x1,%rdx
   0x0000000000049fe4 <+36>:	movzbl (%rdi,%rdx,1),%eax
   0x0000000000049fe8 <+40>:	movzbl (%rsi,%rdx,1),%ecx
   0x0000000000049fec <+44>:	movzbl (%r8,%rax,1),%eax
   0x0000000000049ff1 <+49>:	movzbl (%r8,%rcx,1),%ecx
   0x0000000000049ff6 <+54>:	cmp    %ecx,%eax
   0x0000000000049ff8 <+56>:	jne    0x49ffe <ap_cstr_casecmp+62>
   0x0000000000049ffa <+58>:	test   %eax,%eax
   0x0000000000049ffc <+60>:	jne    0x49fe0 <ap_cstr_casecmp+32>
   0x0000000000049ffe <+62>:	sub    %ecx,%eax
   0x000000000004a000 <+64>:	ret
End of assembler dump.

[2] ap_cstr_casecmp() before this commit:
Dump of assembler code for function ap_cstr_casecmp:
   0x000000000004a000 <+0>:	movzbl (%rdi),%eax
   0x000000000004a003 <+3>:	movzbl (%rsi),%edx
   0x000000000004a006 <+6>:	lea    0x3d533(%rip),%r8        # 0x87540 <ucharmap>
   0x000000000004a00d <+13>:	mov    %rdi,%r9
   0x000000000004a010 <+16>:	mov    %rax,%rcx
   0x000000000004a013 <+19>:	movswl (%r8,%rdx,2),%edx
   0x000000000004a018 <+24>:	movswl (%r8,%rax,2),%eax
   0x000000000004a01d <+29>:	sub    %edx,%eax
   0x000000000004a01f <+31>:	jne    0x4a052 <ap_cstr_casecmp+82>
   0x000000000004a021 <+33>:	mov    $0x1,%edx
   0x000000000004a026 <+38>:	test   %ecx,%ecx
   0x000000000004a028 <+40>:	je     0x4a052 <ap_cstr_casecmp+82>
   0x000000000004a02a <+42>:	nopw   0x0(%rax,%rax,1)
   0x000000000004a030 <+48>:	movzbl (%r9,%rdx,1),%eax
   0x000000000004a035 <+53>:	movzbl (%rsi,%rdx,1),%ecx
   0x000000000004a039 <+57>:	add    $0x1,%rdx
   0x000000000004a03d <+61>:	mov    %rax,%rdi
   0x000000000004a040 <+64>:	movswl (%r8,%rcx,2),%ecx
   0x000000000004a045 <+69>:	movswl (%r8,%rax,2),%eax
   0x000000000004a04a <+74>:	sub    %ecx,%eax
   0x000000000004a04c <+76>:	jne    0x4a052 <ap_cstr_casecmp+82>
   0x000000000004a04e <+78>:	test   %edi,%edi
   0x000000000004a050 <+80>:	jne    0x4a030 <ap_cstr_casecmp+48>
   0x000000000004a052 <+82>:	ret
End of assembler dump.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1897101 13f79535-47bb-0310-9956-ffa450edef68