Revert "make: Define default rule for .c when V=1 or V=2"

This reverts commit 283d88c46c1d4d2ae65f0a3eaf582d0c124d37db as:
- it wrongly assumes the default V=0 (V=1 is the default);
- the new rule broke js2x;
- does not really solve the original problem of printing partial
filenames in gcc error messages.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>