column: fix compilation when libc lacks wide-character support

Commit 4762ae9d removed mtsafe_strtok() but left behind calls to wcstok
and wcspbrk. This leads to build failures when libc does not have the
wide-character functions, like some uClibc builds.

Solve the problem by using strtok_r and strpbrk when HAVE_WIDECHAR is
not defined.

Fixes:
  http://autobuild.buildroot.net/results/fd8a1a8e0cef3aeed9588540e8e663664f6b43aa
  http://autobuild.buildroot.net/results/5ad73ea8b471321988c50d80a5e50d4504151dd6
  http://autobuild.buildroot.net/results/04411b7280dc51ecd51236967981a42352bbeb3e



Signed-off-by: Carlos Santos <casantos@datacom.ind.br>