Removing useless bytecode instructions 'RESERVE 0' and 'ADDTOP 0'
Adding several functions to interact with environment variables.

In addition to removing the superfluous 'isNullString' function,
now that I understand the FFI a bit better, there is a new
'getEnvPair' function that looks into the 'const char** environ'.
Setting, unsetting, and listing all of the environment variables is
now supported.
Merge pull request #490 from gabemc/issue/121

Removing useless bytecode instructions 'RESERVE 0' and 'ADDTOP 0'
Merge pull request #491 from gabemc/feature/environment

Adding several functions to interact with environment variables.
Merge branch 'master' of github.com:edwinb/Idris-dev
Fixed doc comments in multi-line comments bug
Fixed unspecified error on empty module without any declarations