Fix a few more warnings in clang

Fix a few more warnings in clang

Remove unnecessary std


Avoid implicit sign conversion: size_t vs. ssize_t


Avoid implicit sign change by doing it explicitly


Avoid deprecated access declarations

"According the ANSI/ISO Standard, the use of access declarations
is considered deprecated. Instead, you should use a using
declaration for that purpose"
  http://www.devx.com/tips/Tip/5707