Kill checks in configure.ac that aren't used

Summary: They are checks that aren't actually used anywhere to guard anything, so kill them. Many are for things that have long since been standard, or aren't even used.

Reviewed By: yfeldblum

Differential Revision: D4615947

fbshipit-source-id: 2179caff4ef8583c89efedbff3136ae5fc552424

folly/configure.ac

@@ -160,7 +160,7 @@ AM_PATH_PYTHON
 
 # Checks for header files.
 AC_HEADER_STDC
-AC_CHECK_HEADERS([fcntl.h features.h inttypes.h limits.h stdint.h stdlib.h string.h sys/time.h unistd.h mutex.h malloc.h bits/functexcept.h bits/c++config.h])
+AC_CHECK_HEADERS([features.h malloc.h bits/functexcept.h bits/c++config.h])
 
 AC_CHECK_HEADER(double-conversion/double-conversion.h, [], [AC_MSG_ERROR(
                 [Couldn't find double-conversion.h, please download from \
@@ -182,7 +182,6 @@ AC_ARG_WITH([jemalloc], [
 ])
 
 # Checks for typedefs, structures, and compiler characteristics.
-AC_HEADER_STDBOOL
 AC_C_CONST
 AC_C_INLINE
 AC_TYPE_SIZE_T
@@ -210,7 +209,7 @@ static_assert(
   fi
 fi
 
-AC_CHECK_TYPES([ptrdiff_t, pthread_spinlock_t])
+AC_CHECK_TYPES([pthread_spinlock_t])
 
 AC_CACHE_CHECK(
   [for ifunc support],
@@ -542,13 +541,7 @@ AC_DEFINE_UNQUOTED(
    otherwise define to 0])
 
 # Checks for library functions.
-AC_CHECK_FUNCS([getdelim \
-                gettimeofday \
-                memmove \
-                memset \
-                pow \
-                strerror \
-                malloc_size \
+AC_CHECK_FUNCS([malloc_size \
                 malloc_usable_size \
                 memrchr \
                 pipe2 \