Implement default gem info to use when there is no depending gem is defined.
Merge pull request #2108 from take-cheeze/default_gem_info

Implement default gem info to use when there is no depending gem loaded.
Fix MSVC warning for gc.c
Merge pull request #2111 from kyab/fix_msvc_warning_gc.c

Fix MSVC warning for gc.c
Update documentation of `MRuby::Gem::Specification#add_dependency`.
Merge pull request #2113 from take-cheeze/add_dependency_doc

Update documentation of `MRuby::Gem::Specification#add_dependency`.
Add Array#bsearch
Array#fill fix bug when argument use range object
Array#fill use `kind_of?` instead of `respond_to?`
Remove attention about mrbgem dependecy.
Fix MSVC warning for backtrace.c
Merge pull request #2116 from take-cheeze/remove_attention

Remove attention about mrbgem dependecy.
mrb_range_new excl flag use mrb_bool insteard of int
range_init argument for exclude_end use mrb_bool
Merge pull request #2115 from ksss/ary-fill

Fix Array#fill bug and behavior
Range#each fixnums are special
Add Array#delete_if
Merge pull request #2120 from suzukaze/add-array.delete_if

Add Array#delete_if
Merge pull request #2119 from ksss/range-each

Range#each fixnums are special
remove -Wsign-compare warnings