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.
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
Merge pull request #2117 from kyab/fix_msvc_warning_backtrace.c

Fix MSVC warning for backtrace.c
eliminate plain int except for a few cases like arena_index
better integer size assertion suggested by usak
resolve conflict