do not free() stack allocated buffer

use lstat() for WebDAV DELETE, COPY, and MOVE to handle symlinks

opening files fixes:

*) use non-blocking open() not to hang on FIFO files, etc.
*) do not log misleading errno in "not a regular file" error

signal processing stability:

*) use sys_errlist[] in signal handler instead
   of non Async-Signal-Safe strerror_r()
*) do not update time in the timer signal handler,
   since localtime_r() is not Async-Signal-Safe function
*) use previously cached GMT offset value to update time from a signal handler
*) change ngx_time_update() interface since there are no notification methods
   those return time
*) introduce ngx_time_sigsafe_update() to update the error log time only
*) change ngx_time_update() interface

Win32 fixes:

*) compare long file names in case-insensitive mode,
   the bug had been introduced in r3436
*) test default NTFS stream "::$DATA"

cache related fixes:

*) do not pass buf with empty cached response,
   this fixes "zero size buf in output" alert
*) hide cacheable Set-Cookie and P3P FastCGI response headers
*) test comma separator in "Cache-Control"
*) a cache manager thread handle was overwritten by a cache loader thread
   handle, this caused an exit delay, the bug had been introduced in r3248
*) fix handling cached HTTP/0.9 response
*) log proxied HTTP/0.9 responses status as "009"
*) fix the "If-None-Match" header name
*) fix a cached zero-length body case

      r3202, r3203, r3383, r3388, r3417, r3418:

Win32 (mostly) and some Unix file related fixes:

*) preserve errno while ngx_free()
*) win32 ngx_file_info() utf8 support
*) delete Win95 code
*) log file name for read/write errors
*) test incomplete WriteFile()
*) handle short pwrite() to log an error cause: ENOSPC, EDQUOT, or EFBIG
*) uniform ngx_directio_on/off() interface with other file functions
*) do not create Win32 drive letter in ngx_create_full_path()
*) ignore EACCES errors for top level directories in ngx_create_full_path()
*) fix Win32 error messages when an temporary file replaces an existent file:
   *) do not rename an already renamed file
   *) now ngx_win32_rename_file() returns error code
   *) do not log failure inside ngx_win32_rename_file()
*) fix Win32 error message when an temporary file replaces an existent file:
   return at once if ngx_win32_rename_file() was not failed
   and do not try to delete already the renamed temporary file
*) skip URI trailing spaces under Win32
*) disable Win32 short file names

ngx_http_autoindex_module fixes:

*) reset cached dirent.d_type after stat()
   this fixes slash after link to a directory in ngx_http_autoindex_module;
*) use cached dirent.d_type as hint on all systems

   the issues has been introduced in r2235

*) fix ngx_utf8_cpystrn(): it did not fully copy utf-8 string

allow cross device temporary files atomic copying

cache management fixes:

*) separate cache loader process
*) use real file cache length, this fixes cache size counting for responses
   without "Content-Length" header and 304 responses.