What is the Drupal API for reading Drupal configuration files (.info .make etc.)?
You want drupal_parse_info_format.


  Data should be in an .ini-like format to specify values. White-space
  generally doesn't matter, except inside values.


  key = value
  key = "value"
  key = 'value'
  key = "multi-line
  value"
  key = 'multi-line
  value'
  key
  =
  'value'



  Arrays are created using a HTTP GET alike syntax:


  key[] = "numeric array"
  key[index] = "associative array"
  key[index][] = "nested numeric array"
  key[index][index] = "nested associative array"



  PHP constants are substituted in, but only when used as the entire
  value. Comments should start with a semi-colon at the beginning of a
  line.


I actually know this because the Profiler module uses it to parse out its .info file for profile configurations.