Warnings on Perl 5.8.8 when running make

[atoomic]

I noticed these warnings on CentOS 5 using Perl 5.8.8, while testing Devel-PPPort-3.58_01

Steps to reproduce: make clean; perl Makefile.PL && make

# 3.58_01
In file included from RealPPPort.xs:144:
ppport.h: In function ‘DPPP_my_pv_escape’:
ppport.h:16765: warning: pointer targets in passing argument 3 of ‘DPPP_my_utf8_to_uvchr_buf’ differ in signedness
RealPPPort.c:458:1: warning: "croak_xs_usage" redefined
In file included from RealPPPort.xs:144:
ppport.h:14010:1: warning: this is the location of the previous definition
RealPPPort.xs: In function ‘XS_Devel__PPPort_isUTF8_CHAR’:
RealPPPort.xs:3684: warning: passing argument 2 of ‘Perl_is_utf8_string’ discards qualifiers from pointer target type
RealPPPort.c: At top level:
ppport.h:14017: warning: ‘DPPP_my_croak_xs_usage’ defined but not used

I can see similar issues with 3.58, they are not new

#3.58
In file included from RealPPPort.xs:144:
ppport.h: In function ‘DPPP_my_pv_escape’:
ppport.h:10559: warning: pointer targets in passing argument 3 of ‘DPPP_my_utf8_to_uvchr_buf’ differ in signedness
RealPPPort.c:458:1: warning: "croak_xs_usage" redefined
In file included from RealPPPort.xs:144:
ppport.h:7806:1: warning: this is the location of the previous definition
RealPPPort.xs: In function ‘XS_Devel__PPPort_isUTF8_CHAR’:
RealPPPort.xs:3676: warning: passing argument 2 of ‘Perl_is_utf8_string’ discards qualifiers from pointer target type
RealPPPort.c: At top level:
ppport.h:7813: warning: ‘DPPP_my_croak_xs_usage’ defined but not used

[atoomic]

fixed the croak_xs_usage warning via Perl/perl5#18041