Allow inline C code.

[v0dro]

A new directive called C_INLINE should allow the user to directly write C code inside a Rubex file which will be directly copied into the resulting C code as-is. The opening and closing of this section will be demarcated on similar lines as flex's %{ ... %} directive for demarcating code sections.

The code inside this section will not be parsed with the Rubex compiler. Syntax correctness is the programmer's responsibility.

Code sample:

def meth
  int a = 4
  C_INLINE<<
    float b = 5;
    printf("%d", b);
  <<C_INLINE
end