Update anagram to no longer undefine macros for character testing

[dtarditi]

On Linux, functions such as isalpha are turned into macros. The macros make function calls that return pointers to pointers to integers. We don't have enough functionality for Checked C implemented yet to annotate the functions called by those macros so that they can be used in checked code. As a work around, we undefined the macros in anagram so that the original library functions are called. When we do have enough functionality implemented, we should update the headers for Linux to annotate the functions called by the macros and undo the workaround in anagram.