Rmove ELF magic for application/x-sharedlib, generalize x-executable magic.

PIE executables have the same header as ELF shared libs and therefore
were being detected as shared libraries.

The magic for executables was too specific, I removed the check
for the value at offset 16 since it's actually 3 for /usr/bin/ls, not 2.

Fixes gitlab issue #11.
1 job for master in 1 minute and 32 seconds (queued for 1 second)
Status Job ID Name Coverage
passed #3088528