Comments only, no change to functionality

some newer systems have debug sections compressed by default, which
includes those in the crt[1in].o startup files.  These can't simply
be concatenated like all others (which leads to invalid section contents
ultimately making gdb fail) but need special handling.

Instead of that special handling (decompressing, which in turn requires
linking against zlib) let's just ignore such sections, even though that
means to also ignore all other debug sections from that particular input
file.  Our own generated files of course don't have the problem.

Fill in relocs_info table for C67 and fix R_C60_NUM value to really be
greater than all relocation values known to TCC.

C standard specifies that array should be declared with a non null size
or with * for standard array. Declaration of relocs_info in tcc.h was
not respecting this rule. This commit add a R_NUM macro that maps to the
R_<ARCH>_NUM macros and declare relocs_info using it. This commit also
moves all linker-related macros from <arch>-gen.c files to <arch>-link.c
ones.

Catch top level redeclarations too.

Also fix mistakes in tcctest.c and the tcc sources (win32)
showing up now.

R_386_GOT32X can occur in object files assembled by new binutils, and in
particular do appear in glibc startup code (crt*.o). This patch is
modeled after the x86_64 one, handling the new relocation in the same
trivial way.

Whoops, we have our own <elf.h> copy, so I can just as well add
the symbol defines for the relocs instead of hard-coding numbers
in tccelf.c.

 * Documentation is now in "docs".
 * Source code is now in "src".
 * Misc. fixes here and there so that everything still works.

I think I got everything in this commit, but I only tested this
on Linux (Make) and Windows (CMake), so I might've messed
something up on other platforms...