BUG: restore api for file npy_PyFile_Dup and npy_PyFile_DupClose

breaking the api breaks matplotlib build and pip installation.
Introduce npy_PyFile_Dup2 and npy_PyFile_DupClose2 as replacements
Merge pull request #4455 from juliantaylor/api-restore-1.8

restore npy_PyFile_Dup api for 1.8.x