Separated Win16 (USER) and Win32 (MPR) network routines.
Moved implementation of MPR to dlls/mpr/.
Added proper headers and stubs for missing MPR routines.

diff --git a/configure b/configure
index 04fbc2c..25ac0ef 100755
--- a/configure
+++ b/configure
@@ -5473,6 +5473,7 @@
 dlls/imagehlp/Makefile
 dlls/imm32/Makefile
 dlls/lzexpand/Makefile
+dlls/mpr/Makefile
 dlls/msacm/Makefile
 dlls/msacm32/Makefile
 dlls/msnet32/Makefile
@@ -5659,6 +5660,7 @@
 dlls/imagehlp/Makefile
 dlls/imm32/Makefile
 dlls/lzexpand/Makefile
+dlls/mpr/Makefile
 dlls/msacm/Makefile
 dlls/msacm32/Makefile
 dlls/msnet32/Makefile