configure is a generated file, and so should not be edited directly.
You have not told us what version of R these patches were against, but
it looks to me as if wchar.h is included already in current R
(R-patched/R-devel) -- certainly in the second case before wctype.h.
(It really should not be
clang is compiler http://clang.llvm.org, it is fast and better c compiler then
gcc, yesterday i use clang and gfortran compile R.
The only two change in source code is :
1. the configure file (in confiure when test include wctype.h,gcc can compile
but clang need include both wchar.h wctype.h),so
