Clean up compiler warnings and enable them #102

1. 
   gmaxwell commented at 0:10 am on November 13, 2014: contributor

   This doesn’t quite go all the way, in that leaves unused function warnings disabled for the moment.
2. Reorder static to comply with C99 and switch to the inline macro. a4a43d7543
3. Correct function prototypes and avoid unused parameter warnings. 2cad067a36
4. Remove a VERIFY_CHECK for >=0ness on an unsigned type. e28a8b86c7
5. Avoid a shadowed variable. e9e0e21a6f
6. Fix varrious signed/unsigned comparisons. 65a14abb48
7. Avoid unsigned comparison in scalar arith. 850562e3f1
8. Signed/unsigned comparisons in tests. 3276e7d4e2
9. Avoid forward static decl of undefined functions, also fix a paren warning in the tests. f0709ac57e
10. field_gmp's negate doesn't need to use the magnitude argument. 861f9a59cc
11. Enable warnings.

    Wno-unused-function is used for the moment because of the checking
     functions which are currently only used by VERIFY but are not (yet?)
     ifdefed out in normal builds.

    a099073a7e
12. 
    sipa commented at 11:16 am on November 13, 2014: contributor

    utACK
13. sipa merged this on Nov 13, 2014
14. sipa closed this on Nov 13, 2014

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15. sipa referenced this in commit 027eb9c610 on Nov 13, 2014

Contributors
gmaxwell sipa