Unconditionally use explicit_bzero(3)

[alejandro-colomar]

All systems we care about have explicit_bzero(3), and most don't have memset_explicit() at all.

---

Revisions:

v1b

• Rebase

$ git rd 
1:  165359fd6ec2 ! 1:  2b26dd2b14a6 configure.ac, lib/: Don't use memset_explicit()
    @@ configure.ac: AC_CHECK_FUNCS([arc4random_buf \
        updwtmpx innetgr \
        getspnam_r \
        rpmatch \
    --  memset_explicit explicit_bzero stpecpy stpeprintf])
    -+  explicit_bzero stpecpy stpeprintf])
    +-  memset_explicit explicit_bzero stpecpy seprintf])
    ++  explicit_bzero stpecpy seprintf])
      AC_SYS_LARGEFILE
      
      dnl Checks for typedefs, structures, and compiler characteristics.
2:  e819ba044760 ! 2:  12807d5138ce configure.ac, lib/: Unconditionally use explicit_bzero(3)
    @@ configure.ac: AC_CHECK_FUNCS([arc4random_buf \
        updwtmpx innetgr \
        getspnam_r \
        rpmatch \
    --  explicit_bzero stpecpy stpeprintf])
    -+  stpecpy stpeprintf])
    +-  explicit_bzero stpecpy seprintf])
    ++  stpecpy seprintf])
      AC_SYS_LARGEFILE
      
      dnl Checks for typedefs, structures, and compiler characteristics.