GDV-41: [CPP] clang-format to validate/fix style (apache#52)

- added target "make stylecheck" to check style
- added target "make stylefix" to check style
- fixed README.md
- fixed ci script
- used stylefix to fix all existing style violations

Author: pravindra

cpp/src/gandiva/src/cpp/.clang-format

@@ -0,0 +1,6 @@
+---
+Language:        Cpp
+BasedOnStyle:  Google
+ColumnLimit:     90
+...
+

cpp/src/gandiva/src/cpp/CMakeLists.txt

@@ -48,4 +48,5 @@ enable_testing()
 add_subdirectory(src)
 add_subdirectory(integ)
 
-add_lint()  # "make lint" target
+add_stylecheck()  # "make stylecheck" target
+add_stylefix()    # "make stylefix" target

cpp/src/gandiva/src/cpp/README.md

@@ -53,7 +53,14 @@ We follow the [google cpp code style][3]. To validate compliance,
 
 ```shell
 cd debug
-make lint
+make stylecheck
+```
+
+## Fixing code style
+
+```shell
+cd debug
+make stylefix
 ```
 
 [1]: https://brew.sh/