Escape mappings that use '<>' notation.

KeyMap.bind() does not gracefully handle use of '<>' notation.  For
example, trying to call NERDTreeAddKeyMap() with a 'key' argument of
'<Leader>e'.  There were some workarounds KeyMap.bind() to help with
this by specifically allowing you to leave off the '<>' parts for
'<C-...>', '<M-...>' and mouse mappings and it would add them back for
you before creating the mapping.  This commit reverts some of that logic
and simply says that if the key starts with '<', replace it with <lt>.

plugin/NERD_tree.vim

@@ -510,14 +510,18 @@ endfunction
 
 "FUNCTION: KeyMap.bind() {{{3
 function! s:KeyMap.bind()
-    let mapkey = self.key
-    if mapkey =~? '^\([CM]-\|middlerelease\|2-leftmouse\|leftrelease\)'
-        let mapkey = '<' . mapkey . '>'
+    " If the key we're trying to map is a special key we must escape the
+    " leading '<', otherwise vim will replace it with the actual keycode
+    " :he <>
+    if self.key =~# '^<'
+        let keymapInvokeString = substitute(self.key, '^<', '<lt>', '')
+    else
+        let keymapInvokeString = self.key
     endif
 
-    let premap = self.key == "leftrelease" ? " <leftrelease>" : " "
+    let premap = self.key == "<LeftRelease>" ? " <LeftRelease>" : " "
 
-    exec 'nnoremap <buffer> <silent> '. mapkey . premap . ':call <SID>KeyMap_Invoke("'. self.key .'")<cr>'
+    exec 'nnoremap <buffer> <silent> '. self.key . premap . ':call <SID>KeyMap_Invoke("'. keymapInvokeString .'")<cr>'
 endfunction
 
 "FUNCTION: KeyMap.Remove(key, scope) {{{3
@@ -2858,12 +2862,12 @@ endfunction
 function! s:createDefaultBindings()
     let s = '<SNR>' . s:SID() . '_'
 
-    call NERDTreeAddKeyMap({ 'key': 'middlerelease', 'scope': "all", 'callback': s."handleMiddleMouse" })
-    call NERDTreeAddKeyMap({ 'key': 'leftrelease', 'scope': "all", 'callback': s."handleLeftClick" })
-    call NERDTreeAddKeyMap({ 'key': '2-leftmouse', 'scope': "DirNode", 'callback': s."activateDirNode" })
-    call NERDTreeAddKeyMap({ 'key': '2-leftmouse', 'scope': "FileNode", 'callback': s."activateFileNode" })
-    call NERDTreeAddKeyMap({ 'key': '2-leftmouse', 'scope': "Bookmark", 'callback': s."activateBookmark" })
-    call NERDTreeAddKeyMap({ 'key': '2-leftmouse', 'scope': "all", 'callback': s."activateAll" })
+    call NERDTreeAddKeyMap({ 'key': '<MiddleRelease>', 'scope': "all", 'callback': s."handleMiddleMouse" })
+    call NERDTreeAddKeyMap({ 'key': '<LeftRelease>', 'scope': "all", 'callback': s."handleLeftClick" })
+    call NERDTreeAddKeyMap({ 'key': '<2-LeftMouse>', 'scope': "DirNode", 'callback': s."activateDirNode" })
+    call NERDTreeAddKeyMap({ 'key': '<2-LeftMouse>', 'scope': "FileNode", 'callback': s."activateFileNode" })
+    call NERDTreeAddKeyMap({ 'key': '<2-LeftMouse>', 'scope': "Bookmark", 'callback': s."activateBookmark" })
+    call NERDTreeAddKeyMap({ 'key': '<2-LeftMouse>', 'scope': "all", 'callback': s."activateAll" })
 
 
     call NERDTreeAddKeyMap({ 'key': g:NERDTreeMapActivateNode, 'scope': "DirNode", 'callback': s."activateDirNode" })