Fix cp_skip_space return value on whitespace string and add test

[amchoukir]

From the documentation of eat space it should return false if the resulting string is empty. The problem is it compares the return value of cp_skip_space to the beginning of the string rather than the end which will be the return value on a whitespace string. I added a test to confparsetest.cc

[kohler]

Thanks very much for this!