[server] Add a way to append -std=c++11 for the C++ compiler.

By adding a option to the configure script like
$ ./configure --enable-cpp11
The compiler is executed with -std=c++11 option.

Now I won't use entire C++ features. I just want to use 'override'
keyword to avoid the degradation that might happen when change of
the parameter set of a virtual functions are leaked.

For example, when a paramter set of a base class's virtual method
is changed, the paramter set of all overridden methods must also be
changed. Or it won't work as a virtual method.

The present C++ specification doesn't have a mechanism to
detect this problem. However, such kind of the featur has been added
in C++11. It's a 'override' keyword. If this keyword is specified and
it doesn't actually override anything, the compiler causes an error.
[server][Makefile.am] Remove the unnecessary target that was added mistakenly.
[server][DBClientAction] Fix the wrong definition by mistake.
[server][src] Suppress warnings.

This patch suppress the following warnings  that are show
when a option: -std=c++11 is specified.

warning: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wliteral-suffix]
[server][src] Suppress warnings.

This patch suppress the following warnings  that are show
when a option: -std=c++11 is specified.

warning: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wliteral-suffix]
[server][src] Suppress warnings.

This patch suppress the following warnings  that are show
when a option: -std=c++11 is specified.

warning: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wliteral-suffix]
[server][Params.h] Add a mechanism to suppress a warning for the override keyword.

The following declaration causes a warning of the (not C++11) compiler.

void function(int) override
{
    ...

This patch suppress the warning. When we use the compiler with
C++11 features, the 'override' keyword is used and the compiler
checks if it actually overrides a virtual function.
[server][tools] Enaleb C++ features if it's specified.
[server][test/fixtures] Enaleb C++11 features if it's specified.
[server] Enables a 'override' keyword.

If --enable-cpp11 is not specified, it's just ignored by the
macro in Params.h
[server][mlpl] Suppress a warning or an error.
[server][testDBTermCodec] Fix a wrong test label.
[server][testDBTermCodec] Fix the crash on i386 and with C++11 features.

This fix for the problem reported in #216.

Without an explict cast, the number is stacked as 64bit. However,
the code that gets out assumes that the type of the stacked argument
is gint because the type is specified as G_TYPE_INT.
Quote an ambiguous variable in configure.ac
[DBClientHatohol] Add a missing "override" keyword
Merge pull request #217 from project-hatohol/use-c++11

Use c++11