Fix failure to include stdint.h with VS 2010 or newer

[nanis]

See build failure on Windows.

Also, when building from git checkout, Makefile.PL used single quotes to quote author names which upsets cmd.exe. Use double-quotes on Windows.

[salva]

Makefile.PL uses Config::AutoConf to inspect the environment so we can use it to discover if stdint.h is available instead of checking for specific compiler versions.

I have released version 0.52 that does that: https://metacpan.org/release/SALVA/Math-Int64-0.52

Could you test that the issue is actually solved in your environment?

Thank you!

[nanis]

C:\...> cpanm Math::Int64
--> Working on Math::Int64
Fetching http://www.cpan.org/authors/id/S/SA/SALVA/Math-Int64-0.52.tar.gz ... OK
Configuring Math-Int64-0.52 ... OK
Building and testing Math-Int64-0.52 ... OK

Thank you.