A series of patches to better handle local file access

Primary changes are in:
 pydarn/sdio/radDataRead.py 
This introduces the environment variables and logic to correctly support reading the dmap files as stored on disk here at UAF.  Including initial support for extended filenaming such as "kod.d" and "mcm.b" as used by UAF.  All the logic changes are wrapped with environment variable existance tests. If you don't have the new environment variables set, then davitpy falls back gracefully to existing logic.

pydarn/radar/*
edits here make it possible to support radars.sqlite locally without DB access on a multiple user system.  Without these edits, davitpy will attempt to contact VT's DB and will attempt to write radars.sqlite into the davitpy code directory structure. Neither of these are acceptible.  Logic changes wrapped inside test of environment variables as set forth in radDataRead.py. 

 models/aacgm/aacgmlib.c 
harmless backward compatibility check when compiling against older python versions.

 pydarn/dmapio/dmapio.c 
clean up to suppress compiler warning messages about uninitialized values and pointer type mismatches.