Fixes potential writes past the allocated space with mostly
illegal flex array initializers. (60_errors_and_warnings.c
:test_var_array)
In exchange suspicious precautions such as section_reserve
or checks with sec->data_allocated were removed. (There is
an hard check 'init_assert()' for now but it's meant to be
just temporary)
Also, instead of filling holes, always memset(0) structures
& arrays on stack. Sometimes more efficient, sometimes isn't.
At least we can omit putting null initializers.
About array range inititializers: Reparsing tokens has a
small problem with sideeffects, for example
int c = 0, dd[] = { [0 ... 1] = ++c, [2 ... 3] = ++c };
Also, instead of 'squeeze_multi_relocs()', delete pre-existing
relocations in advance. This works even if secondary initializers
don't even have relocations, as with
[0 ... 7] = &stuff,
[4] = NULL
Also, in tcc.h: new macro "tcc_internal_error()"