1) Modify children.c to have search and modification functions for FILE pointer needed by popen/pclose.
2) Switch popen/pclose to use unix pipe(int[]) instead of native PIPE:.
3) Add FILE element in clib4.h line 71.
4) Add popen test in test_programs/.
1) Modify children.c to have search and modification functions for FILE pointer needed by popen/pclose. 2) Switch popen/pclose to use unix pipe(int[]) instead of native PIPE:. 3) Add FILE element in clib4.h line 71. 4) Add popen test in test_programs/.