Update PlainFullTokenizer.lex

include \p{Letter} in the {Identifier} initial character match

Author: Teriand

src/org/opensolaris/opengrok/analysis/plain/PlainFullTokenizer.lex

@@ -41,7 +41,7 @@ super(in);
 %char
 
 //WhiteSpace     = [ \t\f\r]+|\n
-Identifier = [a-zA-Z_] [a-zA-Z0-9_]*
+Identifier = [a-zA-Z\p{Letter}_] [a-zA-Z\p{Letter}0-9\p{Number}_]*
 Number = [0-9]+|[0-9]+\.[0-9]+| "0[xX]" [0-9a-fA-F]+
 Printable = [\@\$\%\^\&\-+=\?\.\:]