mrbgems - remove static RClass

Stop warning in compiling proc.c

proc.c:46: warning: ‘return’ with a value, in function returning void

introduced in f312af11.

refactor OP_RETURN switch to remove a redundant label and avoid goto

fix incorrect checkups in check_iv_name

Added LDFLAGS to Makefiles

Fix memory leak in String#to_i and String#to_f.

mrbgems - Improvements for masuidrive's mobiruby

mrbgems: make calls to every GEM contain now also the include path to the header files of every GEM.

Fix: A GEM with a Dash inside of the name doesn't work.

Mention mrbgems in the README

mrbgems

Fix for issue #569

Keep stack depth and allocation better under control and fix crash on infinite recursion.