* configure.in: Don't do AC_CHECK_HEADERS(wait.h sys/wait.h).
        Instead call AC_HEADER_SYS_WAIT.
        * collect2.c: Don't provide defaults for sys/wait.h macros.
        * gcc.c: Likewise.
        * protoize.c: Likewise.  Also, don't include sys/wait.h.
        * system.h: Include sys/wait.h and provide macro defaults.

From-SVN: r23712