Build breakage on port amd64 due to signal.h

[Paul Goyette <paul%whooppee.com@localhost>]

Found on my continuous build-and-test server, and confirmed with sources 
updated just a few minutes ago...

#   compile  bc/execute.o
/build/netbsd-local/tools/x86_64/amd64/bin/x86_64--netbsd-gcc -O2   -Werror   
-D_POSIX_SOURCE -funsigned-char -I. -I/build/netbsd-local/src/gnu/usr.bin/bc 
-I/build/netbsd-local/src/gnu/dist/bc/bc 
-I/build/netbsd-local/src/gnu/dist/bc/h -nostdinc -isystem 
/build/netbsd-local/dest/amd64/usr/include  -c    
/build/netbsd-local/src/gnu/dist/bc/bc/execute.c
In file included from /build/netbsd-local/dest/amd64/usr/include/signal.h:45,
                 from /build/netbsd-local/src/gnu/dist/bc/bc/execute.c:32:
/build/netbsd-local/dest/amd64/usr/include/sys/signal.h:239: error: expected 
';', ',' or ')' before '*' token
*** [execute.o] Error code 1
nbmake: stopped in /build/netbsd-local/src/gnu/usr.bin/bc



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