Customize clang-format coding styles based on Mozilla template (#770)

Customize clang-format coding styles for C source files based on Mozilla template.
To check whether the C source codes are well formatted:
``` bash
$ cd ${wamr-root}
$ clang-format --Werror --dry-run --style=file path/to/file
```
To format the C source codes in place
``` bash
$ cd ${wamr_root}
$ clang-format -i --style=file path/to/file
```

Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>

.clang-tidy

@@ -0,0 +1,16 @@
+# refer to https://clang.llvm.org/extra/clang-tidy/checks/list.html
+
+Checks:  '-*, readability-identifier-naming, clang-analyzer-core.*,'
+WarningsAsErrors:    '-*'
+HeaderFilterRegex:   ''
+FormatStyle:         file
+InheritParentConfig: false
+AnalyzeTemporaryDtors: false
+User:                wamr
+CheckOptions:
+  - key:             readability-identifier-naming.VariableCase
+    value:           lower_case
+  - key:             readability-identifier-naming.ParameterCase
+    value:           lower_case
+  - key:             readability-identifier-naming.MacroDefinitionCase
+    value:           UPPER_CASE