poco: Remove unnecessary configuration

The configure script automatically detects the type of host.

```
$ uname -a
Darwin pshen01-imac.phage.bcgsc.ca 13.2.0 Darwin Kernel Version 13.2.0: Thu Apr 17 23:03:13 PDT 2014; root:xnu-2422.100.13~1/RELEASE_X86_64 x86_64
$ file /usr/local/opt/poco/bin/*
/usr/local/opt/poco/bin/cpspc:   Mach-O 64-bit executable x86_64
/usr/local/opt/poco/bin/cpspcd:  Mach-O 64-bit executable x86_64
/usr/local/opt/poco/bin/f2cpsp:  Mach-O 64-bit executable x86_64
/usr/local/opt/poco/bin/f2cpspd: Mach-O 64-bit executable x86_64
```