Turn off optimisations when compiling parser

Disabling optimisations in Parser and ParserExpr solves the problem of huge compilation time and memory usage of these two modules. Now they compile in a matter of seconds. I measured compilation time of the largest Idris source files I was able to find in base and it looks that this change doesn't impact performance of the compiler (which is kinda expected - most of compilation time for Idris program probably goes into typechecking).