errno: add ETXTBSY

Add `ETXTBSY` which could be returned by file system reads on some
unixes and emulate it with -148 (`ERROR_PATH_BUSY`) on windows.

include/uv-errno.h

@@ -364,6 +364,12 @@
 # define UV__ETIMEDOUT (-4039)
 #endif
 
+#if defined(ETXTBSY) && !defined(_WIN32)
+# define UV__ETXTBSY (-ETXTBSY)
+#else
+# define UV__ETXTBSY (-4038)
+#endif
+
 #if defined(EXDEV) && !defined(_WIN32)
 # define UV__EXDEV (-EXDEV)
 #else

include/uv.h

@@ -132,6 +132,7 @@ extern "C" {
   XX(ESPIPE, "invalid seek")                                                  \
   XX(ESRCH, "no such process")                                                \
   XX(ETIMEDOUT, "connection timed out")                                       \
+  XX(ETXTBSY, "text file is busy")                                            \
   XX(EXDEV, "cross-device link not permitted")                                \
   XX(UNKNOWN, "unknown error")                                                \
   XX(EOF, "end of file")                                                      \