Squashed 'libs/libinjection/' content from commit 537c705

git-subtree-dir: libs/libinjection
git-subtree-split: 537c7055e56b099ce6af3a9717c9754e79acd09b
Merge commit '01d7df14e416a64c5291ac52db13ecc8fa0f2d83' as 'libs/libinjection'
docs: Update DEVELOPMENT with info on libinjection code.
libs: Add a pre-built libinjection fingerprint header.
modules: Add an experimental sqli module utilizing libinjection.
build: Use absolute directories in RPM build.
all tests: Remove gtest-spi.h include which is unused (except in test_gtest).
Fix distdir target (used by rpm-package target).

Added libinjection to the distribution.
Since libinjection source are included in dist they are marke as nodist
sources for ib_mod_slqli.
docs: Cleanup sqli module docs, and add some credit and links.
modules: Rename sqli module to libinjection to make it more clear where the logic is from.