asan_ignore: Explicitly list ignored behavior fcns

Overflow on signed integers is undefined behavior.  Perl does whatever
the underlying compiler does in this case.  Previously this file used a
wildcard which could specify more functions than we really expect to see
this potential overflow from.  It is safer to mention explicitly all the
functions.

Author: khwilliamson

asan_ignore

@@ -16,8 +16,11 @@
 # suffix with =foo for a "tool-specific category", but neither =undefined
 # nor =signed-integer-overflow worked.
 
-fun:Perl_pp_i_*
-
+fun:Perl_pp_i_add
+fun:Perl_pp_i_divide
+fun:Perl_pp_i_negate
+fun:Perl_pp_i_multiply
+fun:Perl_pp_i_subtract
 
 # this function numifies the field width in eg printf "%10f".
 # It has its own overflow detection, so don't warn about it