Add Change Log file for some non-backward compatible changes in ECP.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@4961 6f19259b-4bc3-4df7-8a09-765794883524

EdkCompatibilityPkg/ChangeLog.txt

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+##########################################################################################
+!!!!!!!!!!!!!!!!!               Notes for this ChangeLog.txt             !!!!!!!!!!!!!!!!!
+
+This log file is used to record two kinds of important information:
+ a) "Non-Compatible Changes": all non-compatible changes should be recorded. These info
+    will help the package user to merge this package; and some non-compatible changes
+    can also be added into release notes as news features when we release this package.
+    Normally Non-Compatible Changes contains the following types:
+      1) Package's external services were changed/updated
+      2) Package's common .h file is renamed, deleted, or the file path is changed.
+      3) The definition of package's common data structure is changed
+      ...
+
+ b) "Important Compatible Changes": some important compatible changes can aslo be recorded
+    in this file, and we can add these updating into release notes when we release this
+    package.
+
+Non-Compatible and Compatible example format:
+==========================================================================================
+EDK_0010: Non-Compatible: owner
+
+	  Class_HFile: PPI A of MdePkg has been removed.
+
+		Code Change :
+		1) Removed the .h file: MdePkg\Include\Ppi\A.h
+
+		Possible Impacts:
+		1) All modules that used this PPI A should be updated.
+
+==========================================================================================
+EDK_0000: Compatible: owner
+
+	  Class_BuildTool: with the EDK_0000 build.exe, the build performance is enhanced great.
+
+		Code Change :
+		1) BaseTools\Bin\Win32\build.exe
+
+!!!!!!!!!!!!!!!!!!                     End of Notes                     !!!!!!!!!!!!!!!!!!
+##########################################################################################
+
+==========================================================================================
+EDK_r4955: Non-Compatible: qhuang8
+	
+	Class_HFile: Update the Device Type Value of MEDIA_FV_DP & MEDIA_FV_FILEPATH_DP.
+	The definitions in MdePkg have already been updated in r4632. This will remove the
+        potential compatibility issues when native EDK II modules & EDK modules built with
+        ECP and run with EDK II core.  
+
+	Code Change:
+	1) Reverse the value of MEDIA_FV_DP & MEDIA_FV_FILEPATH_DP to fix a UEFI errata. 
+
+
+	Possible impact:
+	1) EDK I modules built with this update might not work with old EDK environment. 	
+
+
+==========================================================================================
+EDK_r4960: Non-Compatible: qhuang8
+	
+	Class_HFile: Remove the default value 0xE0000000 of EDKII_GLUE_PciExpressBaseAddress.
+	It now requires platform DSC file to specify it explicitly to avoid runtime issue
+        if they ever uses PciExpressLib in EDK GlueLib.
+        Unlike other default value in GlueLib, this value might not function for all real
+        platforms.   
+
+	Code Change:
+	1) Replace 0xE0000000 to be PCD_EDKII_GLUE_PciExpressBaseAddress. 
+
+	Possible impact:
+	1) If a platform ever uses PciExpressLib in Glue Lib. It needs to explictly specify
+	the value of PCD_EDKII_GLUE_PciExpressBaseAddress for their platform to function.
+	e.g. in EDK II DSC file to build EDK modules: 
+       	[BuildOptions]
+          *_*_*_CC_FLAGS = /D PCD_EDKII_GLUE_PciExpressBaseAddress=0xC0000000
+