test fixnum overflow for add, sub and mul

Fix ISO No.

Rebuild no mrb_open mrbgems test when config file is modified.

Fix Hash test

Add scr_e, to not reassign to e.

Disable C++ exception for chipKIT Max32 example build_config

Update example build_config to include host build setting

Refactor functions in kernel.c

Fix indents in kernel.c

Pacify MSVC warnings for random.c

Fix document generator to remove trailing space in generated document.

Update generated document.

Add comment to Hash#each_pair. And change the line

Add comment about ISO.
Current place is misleading so change line No.

Add comments to Hash methods

Delete unused NameError#new. And add test.

Change to raise TypeError (Hash#merge, #merge!)