The thing is that #include line isn't wrapped in the #ifdef HAVE_OPENCL block, so the file is always included regardless of the OpenCL presence. There are more OpenCL-related bits in miner.h and mine.c which are always compiled.
Did you do ./autogen.sh followed by configure first? If so, what was the output please?
autogen doesn't output anything.
I had to remove the libcurl macro from configure and added the curl flags manually to the generated Makefile since RHEL5 doesn't have libcurl pkgconfig bits.
configure output:
$ CFLAGS="-O3 -Wall -msse2" ./configure
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking target system type... x86_64-unknown-linux-gnu
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether to enable maintainer-specific portions of Makefiles... no
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ANSI C... none needed
checking for style of include used by make... GNU
checking dependency style of gcc... gcc3
checking for ranlib... ranlib
checking how to run the C preprocessor... gcc -E
checking for egrep... grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking minix/config.h usability... no
checking minix/config.h presence... no
checking for minix/config.h... no
checking whether it is safe to define __EXTENSIONS__... yes
checking whether gcc needs -traditional... no
checking whether gcc and cc understand -c and -o together... yes
checking for ranlib... (cached) ranlib
checking sys/mman.h usability... yes
checking sys/mman.h presence... yes
checking for sys/mman.h... yes
checking wchar.h usability... yes
checking wchar.h presence... yes
checking for wchar.h... yes
checking for stdint.h... (cached) yes
checking for mprotect... yes
checking for mmap... yes
checking for MAP_ANONYMOUS... yes
checking whether memchr works... yes
checking whether memmem is declared... yes
checking for memmem... yes
checking whether memmem works... yes
checking for wchar_t... yes
checking whether the preprocessor supports include_next... yes
checking whether system header files limit the line length... no
checking for unsigned long long int... yes
checking for long long int... yes
checking whether stdint.h conforms to C99... yes
checking for C/C++ restrict keyword... __restrict
checking whether memmem is declared without a macro... yes
checking whether mempcpy is declared without a macro... yes
checking whether memrchr is declared without a macro... yes
checking whether rawmemchr is declared without a macro... yes
checking whether stpcpy is declared without a macro... yes
checking whether stpncpy is declared without a macro... yes
checking whether strchrnul is declared without a macro... yes
checking whether strdup is declared without a macro... yes
checking whether strncat is declared without a macro... yes
checking whether strndup is declared without a macro... yes
checking whether strnlen is declared without a macro... yes
checking whether strpbrk is declared without a macro... yes
checking whether strsep is declared without a macro... yes
checking whether strcasestr is declared without a macro... yes
checking whether strtok_r is declared without a macro... yes
checking whether strerror_r is declared without a macro... yes
checking whether strsignal is declared without a macro... yes
checking whether strverscmp is declared without a macro... yes
checking whether memmem works in linear time... no
checking for memmem... (cached) yes
checking whether memmem works... (cached) yes
checking whether NULL can be used in arbitrary expressions... yes
checking for ANSI C header files... (cached) yes
checking syslog.h usability... yes
checking syslog.h presence... yes
checking for syslog.h... yes
checking for working alloca.h... yes
checking for alloca... yes
checking for OpenCL... no
checking for json_loads in -ljansson... no
checking for pthread_create in -lpthread... yes
checking for yasm... /usr/bin/yasm
checking if yasm version is greater than 1.0.1... yes
checking for pkg-config... /usr/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
configure: creating ./config.status
config.status: creating Makefile
config.status: creating compat/Makefile
config.status: creating compat/jansson/Makefile
config.status: creating x86_64/Makefile
config.status: creating lib/Makefile
config.status: creating config.h
config.status: config.h is unchanged
config.status: executing depfiles commands
OpenCL: NOT FOUND. GPU mining support DISABLED.