build-sys: don't install sd-readahead.h as include file, but as documentation

sd-readahead.h is supposed to be a drop-in API, nothing people should
ever link to or could make use without also adding sd-readahead.c to
their sources. Hence, don't install this header file into INCLUDES, but
instead install it as DOCS.

Makefile.am

@@ -2577,7 +2577,8 @@ systemd_readahead_LDADD = \
 	libsystemd-daemon.la \
 	libudev.la
 
-pkginclude_HEADERS += \
+dist_doc_DATA += \
+	src/readahead/sd-readahead.c \
 	src/systemd/sd-readahead.h
 
 rootlibexec_PROGRAMS += \

TODO

@@ -75,8 +75,6 @@ Features:
 
 * Document:
         - PID 1 D-Bus API
-        - Journal C API manual pages
-        - scheduled shutdown API
 
 * introduce Type=pid-file
 
@@ -245,8 +243,6 @@ Features:
 
 * write RPM spec macros for presets
 
-* journal: write man pages for API
-
 * journal: extend hash tables as we go
 
 * journal: API for looking for retrieving "all values of this field"