packaging: use lower case for RC files

The file case doesn't matter. I'm not sure why it is
capitalized.

This is a source of inconsistency between Inno and WiX.
So let's standardize on the lower case names.

The MSI should remove the old files before installing
the new one, so there shouldn't be a problem with a case
collision.

And, users should not have modified these files, so it
should be safe to rename them.

Differential Revision: https://phab.mercurial-scm.org/D7172

contrib/packaging/wix/guids.wxi

@@ -42,8 +42,8 b''
 
   <?define ReadMe.guid = {56A8E372-991D-4DCA-B91D-93D775974CF5} ?>
   <?define COPYING.guid = {B7801DBA-1C49-4BF4-91AD-33C65F5C7895} ?>
-  <?define mercurial.rc.guid = {1D5FAEEE-7E6E-43B1-9F7F-802714316B15} ?>
-  <?define mergetools.rc.guid = {E8A1DC29-FF40-4B5F-BD12-80B9F7BF0CCD} ?>
+  <?define mercurial.rc.guid = {52BBF223-58F6-47F5-9353-8FDEA88D9B8D} ?>
+  <?define mergetools.rc.guid = {5AF0430B-2B76-4BC6-91EE-E771B74A0214} ?>
   <?define ProgramMenuDir.guid = {D5A63320-1238-489B-B68B-CF053E9577CA} ?>
 
 </Include>

contrib/packaging/wix/mercurial.wxs

@@ -75,11 +75,11 b''
 
           <Directory Id='HGRCD' Name='hgrc.d'>
             <Component Id='mercurial.rc' Guid='$(var.mercurial.rc.guid)' Win64='$(var.IsX64)'>
-              <File Id='mercurial.rc' Name='Mercurial.rc' Source='contrib\win32\mercurial.ini'
+              <File Id='mercurial.rc' Name='mercurial.rc' Source='contrib\win32\mercurial.ini'
                     ReadOnly='yes' KeyPath='yes'/>
             </Component>
             <Component Id='mergetools.rc' Guid='$(var.mergetools.rc.guid)' Win64='$(var.IsX64)'>
-              <File Id='mergetools.rc' Name='MergeTools.rc' Source='mercurial\default.d\mergetools.rc'
+              <File Id='mergetools.rc' Name='mergetools.rc' Source='mercurial\default.d\mergetools.rc'
                     ReadOnly='yes' KeyPath='yes'/>
             </Component>
           </Directory>