new is removed from Integer so doesn't need to be removed again in Fixnum
bob doesn't have new so don't undef
Raise a NameError when symbol isn't found.
Add undef var test
Remove incorrect removal of iv
Merge pull request #1275 from carsonmcdonald/undeffix

Fix for 1274
Replace isupper with a macro in msvc
Use casting instead of a macro
Merge pull request #1276 from h2so5/replace-isupper-msvc

Replace isupper with a macro in msvc
restructure header files; move non config lines away from mrbconf.h
add assertion that check sizeof(void*) should be 4 bytes when MRB_NAN_BOXING is in use
Check parameters strictly.

calloc in C99 is expected to return NULL when nelem * len == 0.
Merge pull request #1278 from monaka/pr-calloc-improvement

Check parameters strictly.