Bugfix/fix redundant compiler flags (#658)

* Improved GCC compiler flags in ARM, OS, and test builds. Removed redundant flags, and made them consistent across various builds.

* Fixed redundant redeclaration of various functions detected by change in compiler flags.

* Fixed string truncation warning in bip-init detected by change in compiler flags.

* Fixed some set-but-not-used variables by creating dummy functions instead of using macros.

ports/at91sam7s/CMakeLists.txt

@@ -191,9 +191,20 @@ target_compile_definitions(${EXECUTABLE} PRIVATE
     -DBACAPP_MINIMAL
 )
 
-# inhibit pedantic warnings
 target_compile_options(${EXECUTABLE} PRIVATE
-    -Wall
+    -Wall -Wextra -pedantic
+    -Wfloat-equal -Wconversion -Wredundant-decls 
+    -Wswitch-default
+    # don't warn about conversion, sign, compares, long long and attributes
+    # since they are common in embedded
+    -Wno-sign-conversion 
+    -Wno-conversion
+    -Wno-sign-compare 
+    -Wno-long-long
+    -Wno-attributes
+    # don't warn about implicit fallthrough since it is common in network protocols
+    -Wno-implicit-fallthrough
+    # the older Atmel SDK does not meet coding guidelines
     -Wno-comment
     -Wno-missing-braces
     -Wno-unused-variable