dbghelp: Constify some variables

[Andrew Talbot]

Changelog:
    dbghelp: Constify some variables.

diff --git a/dlls/dbghelp/dwarf.c b/dlls/dbghelp/dwarf.c
index d67c72a..913b0c1 100644
--- a/dlls/dbghelp/dwarf.c
+++ b/dlls/dbghelp/dwarf.c
@@ -2796,7 +2796,7 @@ static void copy_context_reg(CONTEXT *dstcontext, ULONG_PTR dwregdst, CONTEXT* s
     memcpy(ptrdst, ptrsrc, szdst);
 }
 
-static ULONG_PTR eval_expression(struct module* module, struct cpu_stack_walk* csw,
+static ULONG_PTR eval_expression(const struct module* module, struct cpu_stack_walk* csw,
                                  const unsigned char* zp, CONTEXT *context)
 {
     dwarf2_traverse_context_t    ctx;
@@ -2907,7 +2907,7 @@ static ULONG_PTR eval_expression(struct module* module, struct cpu_stack_walk* c
     return stack[sp];
 }
 
-static void apply_frame_state(struct module* module, struct cpu_stack_walk* csw,
+static void apply_frame_state(const struct module* module, struct cpu_stack_walk* csw,
                               CONTEXT *context, struct frame_state *state, ULONG_PTR* cfa)
 {
     unsigned int i;
diff --git a/dlls/dbghelp/image_private.h b/dlls/dbghelp/image_private.h
index b768deb..808f6a1 100644
--- a/dlls/dbghelp/image_private.h
+++ b/dlls/dbghelp/image_private.h
@@ -159,7 +159,7 @@ static inline void image_unmap_section(struct image_section_map* ism)
     }
 }
 
-static inline DWORD_PTR image_get_map_rva(struct image_section_map* ism)
+static inline DWORD_PTR image_get_map_rva(const struct image_section_map* ism)
 {
     if (!ism->fmap) return 0;
     switch (ism->fmap->modtype)
@@ -170,7 +170,7 @@ static inline DWORD_PTR image_get_map_rva(struct image_section_map* ism)
     }
 }
 
-static inline unsigned image_get_map_size(struct image_section_map* ism)
+static inline unsigned image_get_map_size(const struct image_section_map* ism)
 {
     if (!ism->fmap) return 0;
     switch (ism->fmap->modtype)