Compiler warning about function without a proto-type (`get_zeits.c`)

[manodeep]

When compiling with oneAPI, I get a warning about missing prototypes. Looks like the two functions in the file need to have prototypes at the top. Plus, I see that the function definitions are using the old Kernighan-Ritchie style, and not the modern ansi style - going to fix that too.

get_zeits.c:47:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]
   47 | void FC_FUNC(get_zeits,GET_ZEITS)(zts)
      |      ^
../config.h:16:28: note: expanded from macro 'FC_FUNC'
   16 | #define FC_FUNC(name,NAME) name ## _
      |                            ^
<scratch space>:15:1: note: expanded from here
   15 | get_zeits_
      | ^
get_zeits.c:71:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]
   71 | void FC_FUNC(get_ztick,GET_ZTICK)(tic)
      |      ^
../config.h:16:28: note: expanded from macro 'FC_FUNC'
   16 | #define FC_FUNC(name,NAME) name ## _
      |                            ^
<scratch space>:16:1: note: expanded from here
   16 | get_ztick_
      | ^