perf tools: Fix build with perl 5.18

perf tools: Fix build with perl 5.18

perl.h from new Perl release doesn't like -Wundef and -Wswitch-default:

/usr/lib/perl5/core_perl/CORE/perl.h:548:5: error: "SILENT_NO_TAINT_SUPPORT" is not defined [-Werror=undef]
 #if SILENT_NO_TAINT_SUPPORT && !defined(NO_TAINT_SUPPORT)
     ^
/usr/lib/perl5/core_perl/CORE/perl.h:556:5: error: "NO_TAINT_SUPPORT" is not defined [-Werror=undef]
 #if NO_TAINT_SUPPORT
     ^
In file included from /usr/lib/perl5/core_perl/CORE/perl.h:3471:0,
                 from util/scripting-engines/trace-event-perl.c:30:
/usr/lib/perl5/core_perl/CORE/sv.h:1455:5: error: "NO_TAINT_SUPPORT" is not defined [-Werror=undef]
 #if NO_TAINT_SUPPORT
     ^
In file included from /usr/lib/perl5/core_perl/CORE/perl.h:3472:0,
                 from util/scripting-engines/trace-event-perl.c:30:
/usr/lib/perl5/core_perl/CORE/regexp.h:436:5: error: "NO_TAINT_SUPPORT" is not defined [-Werror=undef]
 #if NO_TAINT_SUPPORT
     ^
In file included from /usr/lib/perl5/core_perl/CORE/hv.h:592:0,
                 from /usr/lib/perl5/core_perl/CORE/perl.h:3480,
                 from util/scripting-engines/trace-event-perl.c:30:
/usr/lib/perl5/core_perl/CORE/hv_func.h: In function ‘S_perl_hash_siphash_2_4’:
/usr/lib/perl5/core_perl/CORE/hv_func.h:222:3: error: switch missing default case [-Werror=switch-default]
   switch( left )
   ^
/usr/lib/perl5/core_perl/CORE/hv_func.h: In function ‘S_perl_hash_superfast’:
/usr/lib/perl5/core_perl/CORE/hv_func.h:274:5: error: switch missing default case [-Werror=switch-default]
     switch (rem) { \
     ^
/usr/lib/perl5/core_perl/CORE/hv_func.h: In function ‘S_perl_hash_murmur3’:
/usr/lib/perl5/core_perl/CORE/hv_func.h:398:5: error: switch missing default case [-Werror=switch-default]
     switch(bytes_in_carry) { /* how many bytes in carry */
     ^

Let's disable the warnings for code which uses perl.h.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1372063394-20126-1-git-send-email-kirill@shutemov.name
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>