Fortify builds

[danielealbano]

To improve the overall code quality, stability and security cachegrand should be built using extra options to fortify the builds.

Some work has already been started in an ad hoc branch adding the necessary build options
"-Wall"; "-Wextra"; "-Wpedantic"; "-Wformat=2"; "-Wformat-overflow=2"; "-Wformat-truncation=2";
"-Wformat-security"; "-Wnull-dereference"; "-Wstack-protector"; "-Wtrampolines"; "-Walloca"; "-Wvla";
"-Warray-bounds=2"; "-Wimplicit-fallthrough=3"; "-Wtraditional-conversion"; "-Wshift-overflow=2";
"-Wcast-qual"; "-Wstringop-overflow=4"; "-Wconversion"; "-Warith-conversion"; "-Wlogical-op";
"-Wduplicated-cond"; "-Wduplicated-branches"; "-Wformat-signedness"; "-Wshadow"; "-Wstrict-overflow=4";
"-Wundef"; "-Wstrict-prototypes"; "-Wswitch-default"; "-Wswitch-enum"; "-Wstack-usage=1000000";
"-Wcast-align=strict";
"-D_FORTIFY_SOURCE=2";
"-fstack-protector-strong"; "-fstack-clash-protection"; "-fPIE";
"-Wl,-z,relro"; "-Wl,-z,now"; "-Wl,-z,noexecstack"; "-Wl,-z,separate-code";

It's necessary to resolve all the warnings / errors to be able to merge this branch.