arm: Handle R_ARM_NONE relocs

These relocations are used to express a dependency on a certain
symbol (e.g. for EABIs exception handling to the
__aeabi_unwind_cpp_pr{0,1,2} routines).  Just ignore them in
reloc processing.
tests2: Build executables as well

The individual tests in tests2 are checked only with -run.  Build
(and check) executables as well, to test also building executables.
Git should ignore tests2 executables.
arm: Provide alloca()

This provides a simple implementation of alloca for ARM (and enables
the associated testcase).  As tcc for ARM doesn't contain an assembler,
we'll have to resort using gcc for compiling it.
x86_64: Create proper PLT and GOT also for -run

This makes us use the normal PLT/GOT codepaths also for -run,
which formerly used an on-the-side blob for the jump tables.
For x86_64 only for now, arm coming up.

Conflicts:

	tcc.h
	tccelf.c
arm: Use proper PLT/GOT for -run.

Same as with x86_64, disable the runtime_plt_and_got hack
for -run on arm as well.  For that we need to handle several
relocations as (potentially) generating PLT slots as well.
Tested with mpfr-3.1.2 and gawk (both using --disable-shared),
there are two resp. five pre-existing problems, so no regressions.

This also works toward enabling real shared libs for arm,
but it's not there yet.

Conflicts:

	tccelf.c
ELF: Remove traces of old RUNTIME_PLTGOT code

The last users of it went away, no use in keeping
this code.

Conflicts:

	tcc.h
	tccelf.c
	tccrun.c
win32: warn people about using undeclared WINAPI functions

*** UNCONDITIONALLY ***

Esp. sihce tinycc winapi headers are not as complete as people might
expect this can otherwise lead to obscure problems that are difficult
to debug.

(Originally 'warn_implicit_function_declaration' was set to 1
always for windows but someone must have deleted that line)

Conflicts:

	tccgen.c