Replace int with mrb_bool in parse_string func

Replace int with mrb_bool in local_var_p func

Refactor yylex func

Refactor mrbc_context_new func

Add Kernel#Float

Add Kernel#Hash

Add Kernel#String

instance_methods etc should not include undef'ed method names; based on a patch from @cremno; fix #2613

Refactor mrb_f_array func

Add Kernel.Array

fix typo (i->idx)

fixed. cygwin-gcc(ver4.8.3) warning in conv_digit()

Change mrblib's source path to absolute path

Pacify MSVC warnings for numeric.c, proc.c, and symbol.c

b72e94fa used _etext and _edata to distinguish C string literals from heap allocated strings,
but using _edata, global char arrays may be considered as string literals.  to avoid the issue,
we have to use __init_array_start, which might be less portable.  you can still use _edata, by
using MRB_NO_INIT_ARRAY_START.

on platforms with _etext and _edata, mruby can distinguish string literals so that it avoids memory allocation to copy them.
for example, on my Linux box (x86 32bit), memory consumed by mrbtest decreased from 8,168,203 to 8,078,848 (reduced 88KB).