On a fresh install of CentOS 6.5 using 9.4 RC1 repo and Epel, postgis installs with no errors but I get the following when trying to install extension to into database
gis=# create extension postgis; ERROR: could not load library "/usr/pgsql-9.4/lib/rtpostgis-2.1.so": /usr/pgsql -9.4/lib/rtpostgis-2.1.so: undefined symbol: GDALFPolygonize
It appears there is no longer GDAL 1.92 in the postgresql-9.4 repo, just gdal 1.7 from epel.