remove obsolete notes (#5660)

compiler/DLL-NOTES

-                              The DLL story
-                              -------------
-
-***
-
-This file is intended to be a focal point for notes on how DLLs work. Please
-add cross-references to source and other docs, especially when you don't
-find something here that you need.
-
-***
-
-
-Introduction
-------------
-
-On Windows, DLLs are synonymous with packages (since 4.07; this change
-simplified a rather horrible mess). Hence whenever a module is to be
-compiled to go in a DLL, it must be compiled with -package-name dll-name.
-Typically, failing to do this gives Windows error message boxes of the form
-"The instruction at address <x> tried to read memory at address <x>".
-
-
-Dependencies
-------------
-
-Because references in DLLs must be fully resolved when the DLL is compiled
-(except for references to other DLLs), it is not possible for DLLs to call
-the main program. This means that the parts of the RTS and standard package
-which call the main program cannot be compiled into the relevant DLLs, and
-must instead be compiled as standalone object files and linked in to each
-executable. This gives the following picture of dependencies within a program:
-
-            ___________         ___________
-           |           |------>|           |   GHC-land  |  Application-land
-DLL-land   | HSrts.dll |       | HSstd.dll |             |
-           |___________|<------|___________|             |
-                 |                   ^                   |
------------------|-------------------|-------------------|
-            _____v_____         _____|______             |
-.o-land    |           |       |            |            |
-           |  Main.o   |       | PrelMain.o |-----------------------
-	   |___________|       |____________|            |          |
-                 |                                       |    ______v______
-                 |                                       |   |             |
-                  ------------------------------------------>|   Main.o    |
-                                                         |   |_____________|
-
-(The application's dependencies are not shown.)
-
-
-Bits of the compiler that deal with DLLs
-----------------------------------------
-
-basicTypes/Module.lhs is the most important place, as it deals with which
-modules identifiers are in.
-
-basicTypes/name.lhs, other bits of basicTypes/, nativeGen/, codeGen/,
-abcCSyn/, and even profiling/ have other references.