Make LibDigiDocpp dependency versioned

[glensc]

Fixes #408

cc @metsma

[glensc]

For this to work libdigidocpp.pc needs to provide Version:

For me it's empty:

➔ cat /usr/lib64/pkgconfig/libdigidocpp.pc
prefix=/usr
exec_prefix=/usr/bin
libdir=/usr/lib64
includedir=/usr/include

Name: libdigidocpp
Description: Libdigidocpp C++ library for handling digitally signed documents
Version:
Libs: -L${libdir} -ldigidocpp
Cflags: -I${includedir}

The used DIGIDOCPP_VERSION macro doesn't seem to be defined in libdigidocpp:

[~/rpm/packages/BUILD.x86_64-linux/libdigidocpp-3.13.8(3.8)] ➔ rgrep -r DIGIDOCPP_VERSION .
./etc/Doxyfile.in:41:PROJECT_NUMBER         = @DIGIDOCPP_VERSION@
./src/libdigidocpp.pc.cmake:8:Version: @DIGIDOCPP_VERSION@
[~/rpm/packages/BUILD.x86_64-linux/libdigidocpp-3.13.8(3.8)] ➔

[glensc]

looks like DIGIDOCPP_VERSION was never defined in the project.

at least the initial commit in git repo already has it unreferenced. i suppose the svn history is not available?

[metsma]

It should be probably PROJECT_VERSION
https://cmake.org/cmake/help/v3.13/variable/PROJECT_VERSION.html#variable:PROJECT_VERSION

[metsma]

open-eid/libdigidocpp#260

[glensc]

hmm. it's not fatal error even the version is not satisfied:

-- Found LibDigiDocpp: /usr/lib64/libdigidocpp.so (Required is at least version "3.13.9")
...
➔ grep Ver /usr/lib64/pkgconfig/libdigidocpp.pc
Version: 3.13.8