Build warning.

[vext01]

Today's main (b5933a4):

$ make YK_BUILD_TYPE=release -j4
...
`yk-config release --cc` -O0 -Wall -Wextra -DLUA_COMPAT_5_3 -DLUA_USE_LINUX -DLYK_DEBUG -DUSE_YK -DLUA_USE_JUMPTABLE=0 `yk-config release --cflags --cppflags`   -c -o lyk.o lyk.c
`yk-config release --cc` -O0 -Wall -Wextra -DLUA_COMPAT_5_3 -DLUA_USE_LINUX -DLYK_DEBUG -DUSE_YK -DLUA_USE_JUMPTABLE=0 `yk-config release --cflags --cppflags`   -c -o lauxlib.o lauxlib.c
lvm.c:1181:45: warning: passing 'const Instruction *' (aka 'const unsigned int *') to parameter of type 'Instruction *' (aka 'unsigned int *') discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
 1181 |     YkLocation *ykloc = yk_lookup_ykloc(ci, pc);
      |                                             ^~
./lyk.h:16:56: note: passing argument to parameter 'pc' here
   16 | YkLocation* yk_lookup_ykloc(CallInfo *ci, Instruction *pc);
      |