Rename variable eof to input_eof

Conflicts:
	src/nvim/os/input.c
Add guards for SIGPIPE and SIGQUIT
Add dummy module for unsupported systems
Link against windows libraries
Use putenv for os_setenv

- In systems where setenv is not available, os_setenv() can use
  putenv
Change guard for garray to allow WIN32
FIXME: Use mch_early_init() from os_unix for Dummy

- It seems mch_early_init is completely system independent
FIXME: implement mch_init in dummy