Code cleanups

Code cleanups

https://github.com/google/graphd/issues/8

These all need to be investigated - if you'd like to resolve any of these issues, it would be helpful to produce evidence either for or against these issues.

Completion of error handling

Add more error handling for return values from functions like the following?

• fputs ⇒ gdp_token_printf
• graphd_value_text_strdup ⇒ graphd_smp_status_append_to_list

Reserved Identifier violation

Identifiers like “_ADDB_ACCESS_H” and “__GRAPHD_AST__” do not fit to the expected naming convention of the C language standard.

Unnecessary Null Pointer Checks

Extra null pointer checks are not needed in functions like the following.

• https://github.com/google/graphd/blob/22f110c328acab9cb79c0972c78ff52eb8ef25c2/graphd/graphd-constraint.c#L167
• https://github.com/google/graphd/blob/22f110c328acab9cb79c0972c78ff52eb8ef25c2/libcl/cl-destroy.c#L39