[flac-dev] Include directories

[lvqcl]

Some projects/makefiles add both 'include' and 'include/share'
to the list of additional include directories.

For example, src/share/utf8/utf8.c includes 'include/share/alloc.h'
as "share/alloc.h" but 'include/share/utf8.h' as just "utf8.h".

Also src/share/replaygain_analysis/replaygain_analysis.c includes
"replaygain_analysis.h", not "share/replaygain_analysis.h".

Does it make sense? or is it better to explicitely add "share/" prefix
and remove 'include/share' from the list of include directories?