Fix Issue 4483 - foreach over string or wstring, where element type not specified

core.demangle does not support Unicode and iterates over ASCII only.
Merge pull request #712 from lionello/bug4483

Preparation for issue 4483, specifying foreach char iteration type
OS C functions are nothrow
Merge pull request #742 from WalterBright/nothrow-stat

OS C functions are nothrow
Use malloc and free instead of GC allocating inside (w)string.sort
Merge pull request #746 from yebblies/gcsort

Use malloc and free instead of GC allocating inside (w)string.sort
Issue 3882: Remove pure qualifiers from assumeSafeAppend and _d_arrayshrinkfit prevent calls from being optimized away
Merge pull request #747 from nordlow/warn-unused-returns

Issue 3882: Remove pure qualifier from assumeSafeAppend and _d_arrayshrinkfit
stdarg is nothrow
Merge pull request #745 from WalterBright/nothrow-stdarg

stdarg is nothrow
Fix Issue 12427 - Building druntime with -debug=PRINTF fails.
Merge pull request #748 from AndrejMitrovic/Fix12427

Issue 12427 - Building druntime with -debug=PRINTF fails.
remove gratuitous forward references
this revealed a bad call to onFinalizeError
remove unused forward declarations to gc_*
Merge pull request #750 from rainers/cleanup_adi

remove unused forward declarations to gc_*
Merge pull request #749 from rainers/cleanup_lifetime

[refactor] remove gratuitous forward references in lifetime.d