Add more tests for drfrontend routines

_From [mxm...@gmail.com](https://code.google.com/u/101248221827060668005/) on July 30, 2014 12:00:48_

We have the following list of DR frontend functions that need tests:

1) drfront_access
2) drfront_searchenv
3) drfront_bufprint
4) drfront_tchar_to_char
5) drfront_tchar_to_char_size_needed
6) drfront_char_to_tchar
7) drfront_get_env_var
8) drfront_get_absolute_path
9) drfront_get_app_full_path
10) drfront_is_64bit_app
11) drfront_is_graphical_app
12) drfront_convert_args
13) drfront_cleanup_args
14) drfront_appdata_logdir
15) drfront_string_replace_character
16) drfront_string_replace_character_wide
17) drfront_set_symbol_search_path
18) drfront_sym_init
19) drfront_sym_exit
20) drfront_fetch_module_symbols
21) drfront_create_dir
22) drfront_remove_dir

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1488_