testXHTML: silent jslint about 'inc_dec_within_stmt'

- In-browser jslint does not warn about it.
- It's like C/C++ and 'gcc -Wall' does not warn either.

product/ERP5/tests/jsl.conf

@@ -23,7 +23,7 @@
 +missing_break                # missing break statement
 +missing_break_for_last_case  # missing break statement for last case in switch
 +comparison_type_conv         # comparisons against null, 0, true, false, or an empty string allowing implicit type conversion (use === or !==)
-+inc_dec_within_stmt          # increment (++) and decrement (--) operators used as part of greater statement
+-inc_dec_within_stmt          # increment (++) and decrement (--) operators used as part of greater statement
 +useless_void                 # use of the void type may be unnecessary (void is always undefined)
 +multiple_plus_minus          # unknown order of operations for successive plus (e.g. x+++y) or minus (e.g. x---y) signs
 +use_of_label                 # use of label