Re: fixing missing std:: (see #559)

[ghost]

The original #544 got prematurely closed, appears this is the only way to reopen.

The main criticism of this pull request:

static_cast<int(*)(int)>(std::tolower)

This is due to there being two std::tolower functions:

 std::tolower(int)
charT tolower( charT ch, const locale& loc );

A cast is necessary to tell the compiler to disambiguate which function pointer we are taking.

I propose this change be taken at this time as it resolves the compatibility issues but a new issue should be raised to discuss the best solution as whether to keep, or change to use a function object that calls the std::tolower internally or other viable alternatives.

[nabijaczleweli]

Instead of a function object, you can just have a free catch::tolower() function

[horenmar]

I reimplemented this, because Clara is an external dependency for Catch and should not be changed here + the history was a mess.