This patch simply restores the deleted files unchanged, except for the
following:
o Makefile.ref now generates the js-config.h header file, based on the
values of JS_THREADSAFE and JS_GC_ZEAL it is invoked with.
o The subdirectory containing platform-specific files for Makefile.ref
has been renamed from 'config' to 'ref-config'; the former name
conflicts with the new unified build system. config.mk has been
updated accordingly.
