fix: use of inline keyword is different beyond gnu11; removed inline …

[ffranr]

fix: use of inline keyword is different beyond gnu11; removed inline keyword, compiler optimization O3 should inline if possible

[ffranr]

Links to support this fix:

• https://stackoverflow.com/questions/19068705/undefined-reference-when-calling-inline-function
• https://gcc.gnu.org/onlinedocs/gcc/Inline.html#Inline
• https://stackoverflow.com/questions/16245521/c99-inline-function-in-c-file/16245669#16245669