Fixing clang compilation and supporting clang-tidy

- clang.c includes necessary functions to make clang compiler work (tested on teensy 3.1)
- Added support code to generate a compile_commands.json for clang-tidy
  * Updates the symlink whenever cmake or make is called (Unix OSs only)

.clang-tidy

@@ -0,0 +1,16 @@
+---
+Checks:          'clang-diagnostic-*,clang-analyzer-*,-clang-analyzer-alpha*'
+HeaderFilterRegex: ''
+AnalyzeTemporaryDtors: false
+User:            hyatt
+CheckOptions:    
+  - key:             google-readability-braces-around-statements.ShortStatementLines
+    value:           '1'
+  - key:             google-readability-function-size.StatementThreshold
+    value:           '800'
+  - key:             google-readability-namespace-comments.ShortNamespaceLines
+    value:           '10'
+  - key:             google-readability-namespace-comments.SpacesBeforeComments
+    value:           '2'
+...
+