fix build error for VC++ 2013

fix following compilation error:
45>C:\mrnwork\powershell\work\source\include\mysql/psi/mysql_file.h(541):
error
C3861: 'fgets': identifier not found
...
Merge pull request #10 from cosmo0920/fix-build-for-vc2013

fix build error for VC++ 2013

Patch by cosmo0920. Thanks!!!