FindBZip2: Search locations in GnuWin32 registry

The GnuWin32 "bzip2" installer stores in the registry key

 HKEY_LOCAL_MACHINE\SOFTWARE\GnuWin32\Bzip2

an "InstallPath" value.  Use this entry as a search location.

Modules/FindBZip2.cmake

@@ -22,11 +22,15 @@
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
 
-FIND_PATH(BZIP2_INCLUDE_DIR bzlib.h )
+SET(_BZIP2_PATHS PATHS
+  "[HKEY_LOCAL_MACHINE\\SOFTWARE\\GnuWin32\\Bzip2;InstallPath]"
+  )
+
+FIND_PATH(BZIP2_INCLUDE_DIR bzlib.h ${_BZIP2_PATHS} PATH_SUFFIXES include)
 
 IF (NOT BZIP2_LIBRARIES)
-    FIND_LIBRARY(BZIP2_LIBRARY_RELEASE NAMES bz2 bzip2 )
-    FIND_LIBRARY(BZIP2_LIBRARY_DEBUG NAMES bzip2d )
+    FIND_LIBRARY(BZIP2_LIBRARY_RELEASE NAMES bz2 bzip2 ${_BZIP2_PATHS} PATH_SUFFIXES lib)
+    FIND_LIBRARY(BZIP2_LIBRARY_DEBUG NAMES bzip2d ${_BZIP2_PATHS} PATH_SUFFIXES lib)
 
     INCLUDE(${CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
     SELECT_LIBRARY_CONFIGURATIONS(BZIP2)