AM_CFLAGS no longer in the manual

[NightStrike]

I was looking in the manual to see what the default definition of
AM_CFLAGS was.  It's gone.  Instead, all I see is this:

AM_CFLAGS
This is the variable the Makefile.am author can use to pass in
additional C compiler flags. It is more fully documented elsewhere. In
some situations, this is not used, in preference to the per-executable
(or per-library) _CFLAGS.



It's not more fully documented elsewhere, though.  AM_CPPFLAGS right
about it is, however, fully documented right in this section.  This
should be fixed, since nowhere does the manual say that AM_CFLAGS is
"-g -O2" by default.