[Bug libstdc++/67112] New: [MinGW64] build failure due to name conflict with system headers

[sliwa at ifpan dot edu.pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67112

            Bug ID: 67112
           Summary: [MinGW64] build failure due to name conflict with
                    system headers
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sliwa at ifpan dot edu.pl
  Target Milestone: ---

Created attachment 36118
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36118&action=edit
proposed path

libstdc++ fails to build on MinGW64 due to a name conflict:

* the macro "C" is #defined to the character type for which classes templates
are being instantiated

* the name "C" is used as the name of a field in a struct in winnt.h (a MinGW
system header file)

The attached patch changes the name of the parameter macro to "CHARC".