Remove merge tools irrelevant to a Debian system and RCS merge and add vimdiff

diff -r 196d40e7c885 contrib/mergetools.hgrc
--- a/contrib/mergetools.hgrc
+++ b/contrib/mergetools.hgrc
@@ -12,8 +12,8 @@
 gvimdiff.regname=path
 gvimdiff.priority=-9
 
-merge.checkconflicts=True
-merge.priority=-10
+vimdiff.args=$local $other $base
+vimdiff.priority=-10
 
 gpyfm.gui=True
 
@@ -38,26 +38,11 @@
 p4merge.gui=True
 p4merge.priority=-8
 
-tortoisemerge.args=/base:$base /mine:$local /theirs:$other /merged:$output
-tortoisemerge.regkey=Software\TortoiseSVN
-tortoisemerge.checkchanged=True
-tortoisemerge.gui=True
-
 ecmerge.args=$base $local $other --mode=merge3 --title0=base --title1=local --title2=other --to=$output
 ecmerge.regkey=Software\Elli\xc3\xa9 Computing\Merge
 ecmerge.gui=True
 
-filemerge.executable=/Developer/Applications/Utilities/FileMerge.app/Contents/MacOS/FileMerge
-filemerge.args=-left $other -right $local -ancestor $base -merge $output
-filemerge.gui=True
-
 beyondcompare3.args=$local $other $base $output /ro /lefttitle=local /centertitle=base /righttitle=other /automerge /reviewconflicts /solo
 beyondcompare3.regkey=Software\Scooter Software\Beyond Compare 3
 beyondcompare3.regname=ExePath
 beyondcompare3.gui=True
-
-winmerge.args=/e /u /dl local /dr other /wr $local $other $output
-winmerge.regkey=Software\Thingamahoochie\WinMerge
-winmerge.regname=Executable
-winmerge.checkchanged=True
-winmerge.gui=True