optionGetValue - get a specific value from a hierarcical list

       This  routine  will find an entry in a nested value option or configurable.  If "valueName" is NULL, then
       the first entry is returned.  Otherwise, the first entry with a name that exactly  matches  the  argument
       will  be  returned.   If  there is no matching value, NULL is returned and errno is set to ENOENT. If the
       provided option value is not a hierarchical value, NULL is also returned and errno is set to EINVAL.

       pOptValue
              a hierarchcal value

       valueName
              name of value to get

       The returned result is NULL and errno is set:

       EINVAL - the pOptValue does not point to a valid hierarchical option value.

       ENOENT - no entry matched the given name.  @end itemize

       optionGetValue - get a specific value from a hierarcical list

       a compound value structure

       The info documentation for the -lopts library.
       ao_string_tokenize(3), configFileLoad(3), optionFileLoad(3), optionFindNextValue(3),  optionFindValue(3),
       optionFree(3),    optionLoadLine(3),    optionMemberList(3),    optionNextValue(3),   optionOnlyUsage(3),
       optionPrintVersion(3),      optionPrintVersionAndReturn(3),      optionProcess(3),      optionRestore(3),
       optionSaveFile(3),    optionSaveState(3),    optionUnloadNested(3),    optionVersion(3),    strequate(3),
       streqvcmp(3), streqvmap(3), strneqvcmp(3), strtransform(3),

                                                   2018-08-26                                  optionGetValue(3)

       #include <your-opts.h>
       cc [...] -o outfile infile.c -lopts [...]

       const tOptionValue * optionGetValue(const tOptionValue * pOptValue, char const * valueName);