Enable support for php-fpm on 5.4++ by default

php 5.4 and above have a builtin fast process manager (php-fpm), which can serve as both a webserver and a suitable standin for a fastcgi daemon. php-fpm is enabled by default in 5.4 and above, however, the resulting php-fpm binary is installed in sbin/, rather than bin/. This causes phpenv-rehash and phpenv-which to fail to detect it and be included in the PATH, even when php is compiled with the relevant --enable-fpm configure option.

These commits add support to phpenv for binaries in sbin/ and --enable-fpm on php 5.4 and above wherever apache is also enabled.