Fixed tests on Windows (including out-of-tree problems)

Modified tcctest.c so that it uses 'double' in place of 'long double'
with MinGW since this is what TCC does, and what Visual C++ does. Added
an option -norunsrc to tcc to allow argv[0] to be set independently of
the compiled source when using tcc -run, which allows tests that rely on
the value of argv[0] to work in out-of-tree builds.

Also added Makefile rules to automatically update out-of-tree build
Makefiles when in-tree Makefiles have changed.

Makefile

@@ -343,6 +343,8 @@ tar:    tcc-doc.html
 	rm -rf $(TCC-VERSION)
 	git reset
 
+Makefile: $(top_srcdir)/Makefile
+	cp $< $@
 
 .PHONY: all clean tar distclean install uninstall FORCE