https://issues.dlang.org/show_bug.cgi?id=21964

          Issue ID: 21964
           Summary: importC: Error messages have the wrong column
                    information
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: ibuclaw@gdcproject.org

Errors in cparse.d don't pass a `loc` parameter to diagnostic routines, so typically messages end up being on the last column for a line, or on the wrong line entirely.

e.g
---
_Alignas(double)
float alignas_var;
---

emits the following error:
---
test.c(2,1): Error: `_Alignas` not supported
float alignas_var;
^

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