Preliminary buffers implementation
New features:
* Forced GC
* File Errors
* Get- and Set- UnsetEnv mapped to properties
* popen and pclose for communication with forked processes
* preliminary implementation of fpoll
* fgetc
* fflush
* idris_eqPtr
Fixes:
* putchar(int) insteadof putchar(char)
* Thread argument removed from idris_initArgs
Merge branch 'buffers'
finished buffers and implemented system info