Merge pull request #1513 from rainers/doc_mscrt

document new command line switch -mscrt=libname

dcompiler.dd

@@ -649,6 +649,17 @@ dmd -cov -unittest myprog.d
         generate a $(TT .map) file
       )
 
+    $(WINDOWS
+      $(SWITCH $(SWNAME -mscrt)=$(I libname),
+        if building MS-COFF object files with -m64 or -m32mscoff, embed a reference to
+        the given C runtime library $(I libname) into the object file containing `main`,
+        `DllMain` or `WinMain` for automatic linking. The default is $(TT libcmt) 
+        (release version with static linkage), the other usual alternatives are 
+        $(TT libcmtd), $(TT msvcrt) and $(TT msvcrtd).
+        If $(I libname) is empty, no C runtime library is automatically linked in.
+      )
+    )
+
       $(SWITCH $(SWNAME -noboundscheck),
         turns off all array bounds checking, even for safe functions. $(RED Deprecated
         (use $(TT $(SWLINK -boundscheck)=off) instead).)