Clarify when forcing the moves loop

In some cases we want to go direcly to the moves loop
without checking for early return. The patch make this
logic more clear and consistent.

Tested for no regression, passed STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25282 W: 5136 L: 5022 D: 15124

and LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 72007 W: 12133 L: 12095 D: 47779

bench: 9316798
Assorted nitpicking code-style

No functional change.
Retire 'os' flag from Makefile

Appears to be unused

No functional change

Resolves #147
Fix profile build for syzygy

Touch source files under syzygy directory to force recompilation
after collecting profile data.

No functional change

Resolves #149
Avoid searching the TT twice for the same key/position during both probe() AND store().
Just keep the pointer and remove code from tt.cpp
bench: 8055912
Fix spelling only.
Non functional changes requested by Marco.
Fix comment.  Caught by ceebo.
Removing useless !! found by Marco.