mysql.h does not exist

have_header: checking for mysql.h... -------------------- no

"gcc -E -I. -I/usr/lib64/ruby/1.8/x86_64-linux -I.    -I/usr/include/mysql55 -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -D_GNU_SOURCE -D_FILE_OFFSET_BIT
S=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fwrapv -fPIC  -fPIC -g -static-libgcc -fno-omit-frame-pointer -fno-strict-aliasing -DMY_PTHREAD_FASTMUTEX=1 -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexce
ptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fno-strict-aliasing -fno-stack-protector  -fPIC    conftest.c -o conftest.i"
checked program was:
/* begin */
1: #include <mysql.h>
/* end */

$ ls /usr/include/mysql55/
decimal.h   m_ctype.h   my_attribute.h  my_config_x86_64.h  my_getopt.h  my_net.h      mysql_com.h      mysql_embed.h  mysql_version.h  plugin_audit.h     sql_common.h   sslopt-longopts.h
errmsg.h    m_string.h  my_compiler.h   my_dbug.h           my_global.h  my_pthread.h  mysqld_ername.h  mysql.h        my_sys.h         plugin_ftparser.h  sql_state.h    sslopt-vars.h
keycache.h  my_alloc.h  my_config.h     my_dir.h            my_list.h    mysql         mysqld_error.h   mysql_time.h   my_xml.h         plugin.h           sslopt-case.h  typelib.h