src/augmatch.c: include libgen.h
src/augmatch.c: include libgen.h

Fixes: https://github.com/hercules-team/augeas/issues/556

mlichvar/augeas,mlichvar/augeas,hercules-team/augeas,kunkku/augeas,mlichvar/augeas,kunkku/augeas,ptoscano/augeas,ptoscano/augeas,ptoscano/augeas,kunkku/augeas,hercules-team/augeas