Update CMakeLists.txt

Merge pull request #319 from simongog/address318

#318: Added warning if git is not installed

Merge pull request #199 from simongog/k2_treap

Add K^2-Treap Implementation

Merge pull request #136 from xosh/benchmark_lcp

Benchmark lcp

New version.

Merge pull request #116 from xosh/feature_wt

Feature wt

Merge pull request #111 from simongog/tutorial

Tutorial

Merge pull request #42 from mpetri/topk-wt-methods

quantile topk_greedy topk_qprobe intersect added

Added SA sampling strategy dependent on BWT chars.

Strategy sa_bwt_sampling samples every sa_sample_dens
suffix in text order + all suffixes x=SA[i], with
BWT[i] \in BWT_SAMPLE_CHARS.
BWT_SMAPLE_CHARS is expected to be stored in a
serialized int_vector<> in the cache_config with
key sdsl::constant::KEY_SAMPLE_CHAR.