use strcasecmp() instead of stricmp() on cygwin

[hiyuh]

SSIA.
following is snippet from build log,

os/windows_usb.c: In function ‘get_sub_api’:
os/windows_usb.c:747:4: error: implicit declaration of function ‘stricmp’ [-Werror=implicit-function-declaration]
    if (safe_stricmp(tok, usb_api_backend[api].driver_name_list[i]) == 0) {
    ^

following is a proposed fix,

diff --git a/libusb/os/windows_usb.h b/libusb/os/windows_usb.h
index 35fd2f2..4f3de69 100644
--- a/libusb/os/windows_usb.h
+++ b/libusb/os/windows_usb.h
@@ -48,7 +48,7 @@
 #endif

 #if defined(__CYGWIN__ )
-#define _stricmp stricmp
+#define _stricmp strcasecmp
 #define _snprintf snprintf
 #define _strdup strdup
 // _beginthreadex is MSVCRT => unavailable for cygwin. Fallback to using CreateThread

[yselkowitz]

Bug and fix confirmed.