Initialize the global variable_buffer in main() so that it is never
a null pointer. Then invoking variable_expand("") is never needed:
simply use the variable_buffer pointer when we want to restart the
variable buffer. The main point of this simplification is not to
keep a separate pointer to the beginning of the buffer: this is
dangerous because the buffer may be re-allocated. Instead always
use the variable_buffer pointer itself.
* src/variable.h (initialize_variable_output): Publish.
* src/expand.c (initialize_variable_output): Remove static.
* src/main.c (main): Initialize variable_buffer.
* src/file.c (enter_prereqs): Don't call variable_expand("") and
don't save a separate buffer pointer than might be outdated.
(expand_deps): Ditto.
* src/read.c (record_files): Ditto.
* src/remake.c (library_search): Ditto.
Move the source code (other than glob) into the "src" subdirectory.
Update all scripting and recommendations to support this change.
* *.c, *.h, w32/*: Move to src/
* configure.ac, Makefile.am, maintMakefile: Locate new source files.
* Basic.mk.template, mk/*: Update for new source file locations.
* NEWS, README.DOS.template: Update for new locations.
* build.template, build_w32.bat, builddos.bat: Ditto.
* po/POTFILES.in: Ditto
* tests/run_make_tests.pl, tests/scripts/features/load*: Ditto.
* make.1: Move to doc.
* mk/VMS.mk: Add support for building on VMS (hopefully).
* makefile.vms, prepare_w32.bat: Remove.
* SCOPTIONS: Update to define HAVE_CONFIG_H