gwinhttpfile.c: Fix build on Visual Studio
gwinhttpfile.c: Fix build on Visual Studio

Visual Studio, at least the older versions, cannot use L on macros which
are defined as a constant string, plus the L must be applied to all string
literals here.  This does not look nice, but this is life...

endlessm/glib,Distrotech/glib,Distrotech/glib,endlessm/glib,mzabaluev/glib,endlessm/glib,Distrotech/glib,mzabaluev/glib,johne53/MB3Glib,johne53/MB3Glib,MathieuDuponchelle/glib,mzabaluev/glib,MathieuDuponchelle/glib,johne53/MB3Glib,Distrotech/glib,MathieuDuponchelle/glib,endlessm/glib,mzabaluev/glib,johne53/MB3Glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,Distrotech/glib,MathieuDuponchelle/glib,mzabaluev/glib,johne53/MB3Glib