cmake HAVE_FMEMOPEN examples

lpereira/lwan src/samples/smolsite/CMakeLists.txt :1 

check_function_exists(fmemopen HAVE_FMEMOPEN)

soedinglab/hh-suite lib/ffindex/src/ext/CMakeLists.txt :2 

check_function_exists(fmemopen HAVE_FMEMOPEN)