Write an incl program
to do preprocessor-style file inclusions.
incl will print the contents of each file
listed on its command line,
except that it will replace any output line of the form

     #include "f"

with the contents of the file called f. For example,
     
     incl foo bar

will print the contents of files named foo and bar. If the line

     #include "baz.h"

appears in foo, it will be replaced by the contents of baz.h. If the line

     #include "data.txt"

appears in baz.h, it will be replaced with the contents of data.txt.

Your program must check for and diagnose all errors:
for example, failing to open a file,
or not having enough memory to store a line.
Your program must be able to handle thousands of #include lines;
make sure to close each file when you're done reading it.

(Hint: Write a recursive function printcontents()
to print the contents of a file.
printcontents() should have one string argument
giving the name of the file.)