Fix (relevant) warnings produced by http://cppcheck.sourceforge.net.
Most warnings produced were incorrect. The tool does not seem to support some of the C++11 new features.
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Clang++-3.4 is starting to enforce the following item of C++11 standard,
thus it's making lean not compiling:
It's illegal in C++11: §8.3.6.4 [dcl.fct.default]
"If a friend declaration specifies a default argument expression, that
declaration shall be a definition and shall be the only declaration of
the function or function template in the translation unit."
"-Wextra" option turns on the following warnings:
-Wclobbered
-Wempty-body
-Wignored-qualifiers
-Wmissing-field-initializers
-Wmissing-parameter-type (C only)
-Wold-style-declaration (C only)
-Woverride-init
-Wsign-compare
-Wtype-limits
-Wuninitialized
-Wunused-parameter (only with -Wunused or -Wall)
-Wunused-but-set-parameter (only with -Wunused or -Wall)
