fix off-by-one error in attrsym

The allocation size for null-terminated character is lacking.
In actual, it is no problem in most case
because codegen_palloc allocates more a memory size than required size.
fix indent.
Add mruby-bin-mruby-config
mruby command should not execute program on "syntax only option(-c)".
chmod 755
Don't echo empty string. (Remove workaround for windows)
s/\\"/"/g in mruby-config
Fix #1803
add existing include/ directory only
should check crossing C boudary from resume
fix argument spec setting of Kernel.exit method.
this method requires 1 optional argument.
fix mruby command returning EXIT_SUCCESS when program file can't be
opened.
remove unused variable

GLOBAL_RAND_SEED_KEY is no longer used.
Change the position of -L option from MRUBY_LIBS to MRUBY_LDFLAGS
use mrb_int instead of size_t since string length is represented by mrb_int; close #1810
small refactor