psi_file: psi_load strdup's and stores file path
psi_file.h: Include psi.h header
psi.h: Include string.h header
psi_file: Use own internal strdup method

strdup isn't standard C, so we can't always be sure it has a valid
implementation.
psi: Removing params from main

Just to suppress warnings for the time being.
Makefile: Make obj targets depend on headers
Makefile: Tweak build commands (trivial)
Makefile: Change how source files are listed

Makes it easier to see when files are added/removed
Makefile: Change how tests are listed

Similar to bd76519, for the purpose of making it easier to see
added/removed files.
psi_file.h: Add comments for psi_file functions
psi_file: psi_free=>psi_close

Help clarify some of the code.
psi_file: Add psi_read method

Also update file sanity test to read and print out the first 15 bytes
of the given file.
Merge branch 'sanity-test-suite'