* socket.c, rw.c, deprecated.h, validate.h

* socket.c, rw.c, deprecated.h, validate.h
(SCM_VALIDATE_STRING_COPY): Deprecated.  Replaced all uses with
SCM_VALIDATE_STRING plus SCM_I_STRING_CHARS or
scm_to_locale_string, etc.
(SCM_VALIDATE_SUBSTRING_SPEC_COPY): Deprecated.  Replaced as
above, plus scm_i_get_substring_spec.

* regex-posix.c, read.c, random.c, ramap.c, print.c, numbers.c,
hash.c, gc.c, gc-card.c, convert.i.c, backtrace.c, strop.c,
strorder.c, strports.c, struct.c, symbols.c, unif.c, ports.c: Use
SCM_I_STRING_CHARS, SCM_I_STRING_UCHARS, and SCM_I_STRING_LENGTH
instead of SCM_STRING_CHARS, SCM_STRING_UCHARS, and
SCM_STRING_LENGTH, respectively.  Also, replaced scm_return_first
with more explicit scm_remember_upto_here_1, etc, or introduced
them in the first place.