Fix NAMESPACE_DECL locations to be the line of the module declaration.
Implement handling of Imports to emit DW_TAG_imported_module debug info
Fix typo causing build failure when building for a mingw32 target
Add prototype for SetLastError (fixes build, as it is used elsewhere)
Function never fails, return 0 (fixes w32 build)
void gthread_mutex_destroy -> int gthread_mutex_destroy
Merge pull request #72 from Ace17/master

Various build fixes for mingw32 target.
Merge branch 'master' into gdc-4.8