Remove src/Makefile.am.

* src/Makefile.am: Rename as...
	* src/local.mk: this.
	Prefix all the paths with src/.
	(AUTOMAKE_OPTIONS): Build object files in the sub dirs.
	(AM_CPPFLAGS): Find find in builddir/src.
	(YACC): Move the flags into...
	(AM_YFLAGS): here.
	* maint.mk (sc_tight_scope): Disable.
	It used to bounce to the version in src/Makefile.am which is now
	part of this very Makefile.
	* Makefile.am, configure.ac: Adjust.
	* src/scan-code-c.c, src/scan-code.l: We can no longer rely on
	include "..." to find files "here": we are no longer in src/, so
	qualify the includes with src/.
	* doc/Makefile.am (PREPATH): No longer include the top_builddir
	prefix.
	(.x.1): Adjust to be able to create src/foo from the top level
	Makefile, instead of going bounce to src/Makefile the creation of
	foo.

Makefile.am

@@ -17,7 +17,7 @@
 
 ACLOCAL_AMFLAGS = -I m4
 
-SUBDIRS = po runtime-po lib src doc tests
+SUBDIRS = po runtime-po lib . doc tests
 if BISON_CXX_WORKS
 SUBDIRS += examples/calc++
 endif
@@ -33,10 +33,13 @@ EXTRA_DIST = .prev-version .version cfg.mk maint.mk \
   djgpp/subpipe.c djgpp/subpipe.h djgpp/djunpack.bat \
   djgpp/fnchange.lst djgpp/testsuite.sed
 
+# Initialization before completion by local.mk's.
+BUILT_SOURCES =
 include build-aux/local.mk
 include data/local.mk
 include etc/local.mk
 include examples/local.mk
+include src/local.mk
 
 .PHONY: maintainer-check
 maintainer-check:
@@ -59,7 +62,7 @@ maintainer-xml-check:
 # a developer might naively reference .version in a test case while the bison
 # executable still compiles with VERSION, and so the test case might fail or
 # pass incorrectly.
-BUILT_SOURCES = $(top_srcdir)/.version
+BUILT_SOURCES += $(top_srcdir)/.version
 $(top_srcdir)/.version: configure
 	echo $(VERSION) > $@-t && mv $@-t $@
 dist-hook: