Add optional time parameters to touch function

[eugene kirillov]

PHP's built-in touch function has 2 optional parameter:

• time
  The touch time. If time is not supplied, the current system time is used.
• atime
  If present, the access time of the given filename is set to the value of atime. Otherwise, it is set to the value passed to the time parameter. If neither are present, the current system time is used.

These parameters are useful for some common use cases and worth to be added to the lib

[Aaron Piotrowski]

Merged in b67c837. Thanks!