Add Glibc predefined global version and insert all C runtimes into the list of predefined global versions
Get rid of the last usage of std.c, which has been moved to core.sys in druntime
Merge pull request #4111 from joakim-noah/add_glibc

Add predefined global version for Glibc
Improve pretty-printer for the qualified 'string' types
Support human-readable pretty-printing for the UTF16/32 strings