narrow decorator match to exclude matrix multiplication

syntax/python.vim

 " Decorators (new in Python 2.4)
 "
 
-syn match   pythonDecorator	"@" display nextgroup=pythonDottedName skipwhite
+syn match   pythonDecorator	"\(^\s*\)\@<=@" display nextgroup=pythonDottedName skipwhite
 if s:Python2Syntax()
   syn match   pythonDottedName "[a-zA-Z_][a-zA-Z0-9_]*\%(\.[a-zA-Z_][a-zA-Z0-9_]*\)*" display contained
 else