fix #1519

the 128th element in an array literal would trigger a corner case on
splat mode checking, in which mruby will splat an that value into its
parent array. the issue was masked by the fact of ary_concat() also
accept non-array value:

1.9.3p286 :002> a = 1
1.9.3p286 :003> [*a]
 => [1]

the expected behaviour should be OP_ARYPUSH the 128th element, instead of
splat it by OP_ARYCAT.

Remove function delaration not implemented in code

fix build error when ENABLE_DEBUG is defined

fix bugs on Heredocument

eliminate use of traditional intern API (mrb_intern()) completely

- heredoc in array literal
- heredoc in args
- heredoc in expression expand

Use self for the given proc in mrb_yield

Fixed self value in a block is changed with return value

remove executable bit from include/mruby/dump.h file

Fix #1504

fix #1504

Fix checking return value of fread()

Fix insufficient preparation to call mrb_debug_info_append_file.

MSVC: compilation works again (+minor style fixes)

BUG: mrb_irep_free (access of freed memory)