Fix a few compile errors:

Fix a few compile errors:

* Replace use of non-standard integral types (e.g. u_char)
* Convert boost::filesystem::paths to std::strings using the .string()
method rather than .c_str(), because on Windows .c_str() returns a wide
character string, which is not convertible to a std::string.

Change-Id: Ia86b0653697033bb1afa01e64b5b2103dd042ffd
Signed-off-by: Robert Hughes <robert.hughes@arm.com>