doc: First run at texinfo documentation

After much consideration, texinfo was chosen for the Hamlib manual.
Initially Docbook had been considered and then abandoned.  Doxygen
generated output from the source files has filled that role since but
experience has shown that more explanation would be useful.  ASCIIdoc
had been considered and while HTML and PDF outputs are possible, GNU
info style documentation seems not to be.  Texinfo provides for all
three and is easily integrated into Automake and enables version and
update variables generated by Autotools to be easily integrated into the
documentation.

The manual is released under the GNU Free Document License with no
invariant sections and no cover texts.  This meets the current Debian
Free Software Guidelines.

doc/Makefile.am

@@ -3,5 +3,9 @@ EXTRA_DIST = hamlib.cfg index.doxygen hamlib.css footer.html
 SRCDOCLST = ../src/rig.c ../src/rotator.c ../src/tones.c ../src/locator.c \
 		../src/event.c ../src/conf.c ../src/mem.c ../src/settings.c
 
+info_TEXINFOS = hamlib.texi
+
+AM_MAKEINFOHTMLFLAGS = --no-headers --no-split
+
 doc: hamlib.cfg $(SRCDOCLST)
 	doxygen hamlib.cfg