Syntax: Stricter typeface and fix preCode (alias inline) nested in bold

Fix: Syntax bug precode nested in bold apperead bold

Problem:
1. `that_ HERE _was` italic
2. `__that ``HERE`` was__  bold => PreCode should not receive typeface
region changes

Solution:
1. Stricter regex (and add \* to VimwikiError)
2. Add VikiError and WikiPre to nestables syntaxes

test/vimrc

@@ -268,4 +268,10 @@
     return synIDattr(synIDtrans(l:s), 'name')
   endfun
 
+  " Run Assert only if vim version higth enough
+  function! AssertIfVersion(version, one, two)
+    if v:version < a:version | return | endif
+    AssertEqual a:one, a:two
+  endfunction
+
 " vim: ft=vim:sw=2