chmod -x for source files (#557)

chmod -x for source files (#557)

keep `x` for `.pl`, `.sh`, `.bash` and `.git/hooks/*.sample`

```
find . -type f -perm -111

find . -name "*.go" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.s" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.h" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.c" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.f" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.f90" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.json.deflate" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.dat" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.txt" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.md" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.html" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.xml" -type f -perm -111 -exec chmod -x {} \;
find . -name "Makefile" -type f -perm -111 -exec chmod -x {} \;
find . -name "Dockerfile" -type f -perm -111 -exec chmod -x {} \;
find . -name "README" -type f -perm -111 -exec chmod -x {} \;
find . -name "AUTHORS" -type f -perm -111 -exec chmod -x {} \;
find . -name "LICENSE" -type f -perm -111 -exec chmod -x {} \;
find . -name "PATENTS" -type f -perm -111 -exec chmod -x {} \;
find . -name "CONTRIBUTORS" -type f -perm -111 -exec chmod -x {} \;
find . -name "AUTHORS" -type f -perm -111 -exec chmod -x {} \;
find . -name ".gitignore" -type f -perm -111 -exec chmod -x {} \;
find . -name ".gitattributes" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.gz" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.cfg" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.pem" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.key" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.srl" -type f -perm -111 -exec chmod -x {} \;
find . -name "*.crt" -type f -perm -111 -exec chmod -x {} \;
```