TS-2097: remove unsued string functions

first round of removing unsued/useless string functions
TS-2097 replace ink_string_copy() w/ ink_strlcpy()

we already have ink_strlcpy() in our reportoire, and ink_string_copy()
is only used twice. We replace those two occurances.
TS-2097 Remove ink_string_find_dotted_extension()