mes: resurrect full reader in C core.
* module/mes/read-0.mes (defined?): New function.
(eat-whitespace, read-env, read-word, read-block-comment,
read-line-comment, read-list, read-character, read-hex, read-octal,
reader:read-string, lookup, read-hash, read-word): Only define if
not %c-reader.
* module/mes/base-0.mes (defined?): Remove.
* src/mes.c[MES_C_READER]: Set ARENA_SIZE=10000000.
(scm_symbol_quasiquote scm_symbol_unquote,
scm_symbol_unquote_splicing, scm_symbol_syntax,
scm_symbol_quasisyntax, scm_symbol_unsyntax,
scm_symbol_unsyntax_splicing): New symbol.
(scm_symbol_c_reader): New symbol.
(MAKE_KEYWORD)[MES_C_READER]: New define.
(mes_symbols): Define %c_reader.
* src/reader.c (read_word_)[MES_C_READER]: Extend to full Scheme
reader.
(eat_whitespace)[MES_C_READER]: Likewise.
(read_block_comment, read_hash, read_word, read_character,
read_octal, read_hex, append_char, read_string)[MES_C_READER]:
Likewise.
* make.scm (bin.gcc,bin.mescc): Define MES_C_READER=1.