What is the distinction between AC_PROG_CC_C_O and AC_PROG_CC ??

[Bruce Korb]

The index and search of the docs only yields this:

`AM_PROG_CC_C_O'
     This is like `AC_PROG_CC_C_O', but it generates its results in the
     manner required by automake.  You must use this instead of
     `AC_PROG_CC_C_O' when you need this functionality, that is, when
     using per-target flags or subdir-objects with C sources.

Are there better docs in the queue?  Thank you! - Bruce