--enable-silent-warnings now suppresses more chatter.

--enable-silent-warnings now suppresses more chatter.

* INSTALL, etc/NEWS: Document this.
* lib-src/Makefile.in (AM_DEFAULT_VERBOSITY, AM_V_CC, am__v_CC_)
(am__v_CC_0, am__v_CC_1, AM_V_CCLD, am__v_CCLD_, am__v_CCLD_0)
(am__v_CCLD_1): New macros, taken from Automake.
(regex.o, etags${EXEEXT}, ctags${EXEEXT}, ebrowse${EXEEXT})
(profile${EXEEXT}, make-docfile${EXEEXT}, movemail${EXEEXT})
(pop.o, emacsclient${EXEEXT}, emacsclientw${EXEEXT})
(emacsclientw${EXEEXT}, ntlib.o, hexl${EXEEXT})
(update-game-score${EXEEXT}): Use them.
* lwlib/Makefile.in (AM_DEFAULT_VERBOSITY, AM_V_CC, am__v_CC_)
(am__v_CC_0, am__v_CC_1): New macros, taken from Automake.
(.c.o): Use them.
* oldXMenu/Makefile.in (AM_DEFAULT_VERBOSITY, AM_V_CC, am__v_CC_)
(am__v_CC_0, am__v_CC_1): New macros, taken from Automake.
(.c.o): Use them.
* src/Makefile.in (AM_DEFAULT_VERBOSITY, AM_V_CC, am__v_CC_)
(am__v_CC_0, am__v_CC_1, AM_V_CCLD, am__v_CCLD_, am__v_CCLD_0)
(am__v_CCLD_1): New macros, taken from Automake.
(.c.o, .m.o, temacs$(EXEEXT)): Use them.