Description:- Replace, the string replacement utility fails
on the windows platform.

Analysis:- The utility takes files and multiple string
pairs as input. In the windows platform, the utility maps
the standard input incorrectly (Considers 0 as the fd for
standard input instead of 2048 on windows). Hence when the
input file is supplied to the utility due to the incorrect
mapping, a bad file descriptor error is generated causing
the utility to exit with an error.

Fix:- "my_fileno()" is used for getting the correct file
despscriptor for standard input.