Adjust gdb.base/memops-watchpoint.exp for native Windows

Adjust gdb.base/memops-watchpoint.exp for native Windows

On native Windows, I see:

 continue
 Continuing.

 Thread 1 hit Hardware watchpoint 2: -location a[28]

 Old value = 104 'h'
 New value = 0 '\000'
 0x00007ffe640a9953 in msvcrt!memmove () from C:\Windows\System32\msvcrt.dll
 (gdb) FAIL: gdb.base/memops-watchpoint.exp: continue until memset watchpoint hits
 ... two more of the same ...

This fails for a few reasons:

1) thread_prefix_re

  The thread_prefix_re regexp doesn't handle the case of a thread with
  no name:

      set thread_prefix_re "(?:Thread $::decimal \[^\r\n\]* hit )?"
						^          ^

  Note how it expects two spaces between the thread number and the
  "hit" word.

  Fix it by dropping one of the spaces in the regexp.

2) libc vs msvcrt.dll

  This:

	  -re ".*${function_re}.* \\(\\) from .*libc\[^\r\n\]+\r\n" {

  is expecting that the function exists in libc, which is not the case
  on Windows.

  Fix it by not expecting any particular library name.

3) endline consumed when it shouldn't

  All these patterns:

    -re ".*${function_re}.* \\(\\) at .*:$::decimal\r\n" {
    -re ".*${function_re}.* \\(\\) from .*libc\[^\r\n\]+\r\n" {
    -re "in \\?\\? \\(\\) from .*libc\[^\r\n\]+\r\n" {

  ... consume the \r\n, and then do exp_continue, expecting that
  eventually the:

    -re -wrap "" {

  ... pattern matches.  However, if the \r\n is already consumed, then
  -wrap doesn't work, because that expects "\r\n$gdb_prompt ".

  This wasn't noticed on Linux because there GDB prints at least one
  more line before the prompt:

    Old value = 104 'h'
    New value = 0 '\000'
    __memset_avx2_unaligned_erms () at ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:171
    warning: 171    ../sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S: No such file or directory
    (gdb) PASS: gdb.base/memops-watchpoint.exp: continue until memset watchpoint hits
    ...
    Old value = 100 'd'
    New value = 114 'r'
    __memcpy_avx_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:272
    272     in ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S
    (gdb) PASS: gdb.base/memops-watchpoint.exp: continue until memmove watchpoint hits
    ...

  Fix it by expecting but not consuming the endlines.

4) msvcrt.dll implements memset with memmove

  Note how we are expecting a memset hit, but we get a memmove:

    0x00007ffe640a9953 in msvcrt!memmove () from C:\Windows\System32\msvcrt.dll
    (gdb) FAIL: gdb.base/memops-watchpoint.exp: continue until memset watchpoint hits

  We already handle memcpy implemented with memmove and vice versa.
  Fix it by handling memset implemented with memmove in the same way.

With all these fixed, the test now passes cleanly on native Windows.
It still passes cleanly on GNU/Linux.

Change-Id: I1a8a448e3a94d1d6736aca817568b2c0408dc2dc