give Win32 miniperl a real getcwd for build perf

give Win32 miniperl a real getcwd for build perf

getcwd() is now 605x faster for Win32 miniperl.
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use Cwd;
Cwd::getcwd() for(0..10000);
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before
C:\p523\src\win32>timeit -f t.dat ..\miniperl -I..\lib t.pl
Version Number:   Windows NT 6.1 (Build 7601)
Exit Time:        2:03 am, Thursday, December 10 2015
Elapsed Time:     0:01:12.438
Process Time:     0:00:14.289
System Calls:     5802378
Context Switches: 1455066
Page Faults:      5250724
Bytes Read:       76809789
Bytes Written:    5278717
Bytes Other:      10407004
after
C:\p523\src\win32>timeit -f t.dat ..\miniperl -I..\lib t.pl
Version Number:   Windows NT 6.1 (Build 7601)
Exit Time:        1:20 am, Thursday, December 10 2015
Elapsed Time:     0:00:00.119
Process Time:     0:00:00.124
System Calls:     4658
Context Switches: 540
Page Faults:      1127
Bytes Read:       99074
Bytes Written:    0
Bytes Other:      12888