Fix incorrect dependencies in Makefile
Fix bug: rgbasm segfault when \@ is used outside a macro

The problem occurs when \@ is accessed outside the definition of a
macro and is not between "" or {}, or when it is used in an argument of
a macro call, i.e. when the access is processed by PutUniqueArg().

PutUniqueArg(), puts back the string value of \@ to the lexer's buffer
(to substitute \@ by the unique label string).
When \@ is not defined, sym_FindMacroArg(-1) returns NULL, which
yyunputstr() doesn't expect and crashes.

Solution:
Generate an error when \@ is not defined.

Regression test:

SECTION "HOME", HOME
        ld a,\@

Will segfault.
On the fixed version, it will return an error as \@ is not available.
Add assertion to symFindMacroArg() to debug oob array access
Fix out of bounds array access on invalid macro arg references

A reference to an invalid macro argument (\ not followed by a digit
between 1 and 9) will cause an access outside of the bounds of the
currentmacroargs array in sym_FindMacroArg().

Macro arg references are processed in two places:

In CopyMacroArg(): called when scanning tokens between "", {} and
arguments of a macro call. The only problem here is that it accepts \0
as valid and so calls sym_FindMacroArg with a invalid value.

In PutMacroArg(): called by the lexer automata when it encounters a
token matching \\[0-9]? (in other cases than above). So not only it
accepts \0 but also \ alone.
  Memo: In setuplex(), a rule is defined with a regex composed of up to
    three ranges of chars and takes the form:
      [FirstRange]
      or [FirstRange][SecondRange]?
      or [FirstRange]([SecondRange][Range]*)?
    On scanning, when several rules match, the first longuest one is
    choosen.

Regression test:
1)
SECTION "HOME", HOME
	db "\0"

2)
SECTION "HOME", HOME
	db \A

3)
SECTION "HOME", HOME
	db \
Style.
Merge branch 'fix-uniquearg-segfault' of https://github.com/chastai/rgbds
Merge branch 'fix-makefile' of https://github.com/chastai/rgbds
PATH_MAX is not exactly portable. Hack around it for now.