updated the regex of 'alpha*' validation rules

Regex for alphabets was '/^\pL+$/u', which would match almost all 'letters'.
There are some languages in which a 'modifier' is also applicable to the letter, 
adding another '/pM' takes care of this.
added some tests for the updated validation rules
rectified error.
rectified error again
rectified error with AlphaDash
my last commit was a mistake
this is what happens when I try unit testing. :(
Merge pull request #3837 from CurosMJ/master

updated the regex of 'alpha*' validation rules, to support languages with modifiers.