silence some compiler warnings on VC6

sv.c and toke.c have the following warnings on VC6 but not VC 2003
(and probably newer too), example
..\toke.c(3149) : warning C4761: integral size mismatch in argument;
conversion supplied

find_default_stash (commit 90aeefb473 )& gv_magicalize (commit 71c35c050e )
..\gv.c(1680) : warning C4028: formal parameter 6 different from declaration
..\gv.c(1783) : warning C4028: formal parameter 6 different from declaration

not all VC6 compiler warnings are fixed by this patch
[perl #122911] regexp.h: Rmv VOL from op_comp sig

It is no longer needed as of 1067df30ae9.