add doc pvs studio

.pvsconfig

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+//-V::1042

doc/readme-pvs-studio.md

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+# How to integrate PVS-Studio
+
+We obtained a free license of PVS-Studio due to the open source nature of Exiv2.
+
+## CMake integration
+
+To check a project configured with CMake, such as Exiv2, we need to generate the JSON compilation database. 
+
+```bash
+# Under an already configured "buildXXX" directory
+cd buildXXX
+cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ...
+
+# Output file: compile_commands.json
+```
+
+The analysis starts with the following commands:
+
+```bash
+export PVS_LICENSE=~/.config/PVS-Studio/PVS-Studio.lic
+pvs-studio-analyzer analyze -l $PVS_LICENSE -o pvsStudio.log -j8
+plog-converter -a GA:1,2 -t tasklist pvsStudio.log -o pvsStudio.tasks
+plog-converter -a GA:1,2 -t fullhtml pvsStudio.log -o pvsReportHtml
+log-converter -a GA:1,2 -d V1042 -t fullhtml pvsStudio.log -o pvsReportHtml
+```