Update testcases for recent gnu11 changes.

ok for trunk?

thanks.

gcc/testsuite/
   * gcc.target/aarch64/pic-constantpool1.c: Add explicit declaration.
   * gcc.target/aarch64/pic-symrefplus.c: Likewise.
   * gcc.target/aarch64/reload-valid-spoff.c: Likewise.
   * gcc.target/aarch64/vect.x: Likewise.
   * gcc.target/aarch64/vect-ld1r.x: Add return type.
   * gcc.target/aarch64/vect-fmax-fmin.c: Likewise.
   * gcc.target/aarch64/vect-fp.c: Likewise.