Fix compilation with GCC 7.
https://bugs.gentoo.org/635746

--- doxymacs-1.8.0.orig/c/doxymacs_parser.c
+++ doxymacs-1.8.0/c/doxymacs_parser.c
@@ -70,6 +70,7 @@
 
 hash_entry *symbol_hash[HASH_SIZE];
 
+static inline unsigned int hash(const char *s);
 inline unsigned int hash(const char *s)
 {
     unsigned int h = 0;
@@ -82,6 +83,7 @@
     return abs(h % HASH_SIZE);
 }
 
+static inline void AddToHash(completion_list *cl);
 inline void AddToHash(completion_list *cl)
 {
     unsigned int h = hash(cl->symbol);
@@ -96,6 +98,7 @@
 }
 
 /* mmmmm... free hash */
+static inline void FreeHash(void);
 inline void FreeHash(void)
 {
     unsigned int i;
@@ -117,6 +120,7 @@
 
 /* XML Helper Functions */
 
+static inline char *XMLTagChild(xmlNodePtr node, const char *name);
 inline char *XMLTagChild(xmlNodePtr node, const char *name)
 {
     xmlNodePtr cur = node->xmlChildrenNode;
@@ -141,6 +145,7 @@
     return NULL;
 }
 
+static inline char *XMLTagAttr(xmlNodePtr node, const char *attr);
 inline char *XMLTagAttr(xmlNodePtr node, const char *attr)
 {
     xmlAttrPtr props = node->properties;
@@ -167,6 +172,7 @@
 
 /* Look up functions for symbols and descriptions */
 
+static inline completion_list *LookUpSymbol(const char *symbol);
 inline completion_list *LookUpSymbol(const char *symbol)
 {
     unsigned int h = hash(symbol);
@@ -187,6 +193,7 @@
     return NULL;
 }
 
+static inline desc_url_list *LookUpDesc(completion_list *entry, const char *desc);
 inline desc_url_list *LookUpDesc(completion_list *entry, const char *desc)
 {
     desc_url_list *cur = entry->descs;
@@ -206,6 +213,8 @@
 
 /* Add the given name, description and url to our completion list */
 
+static inline int AddToCompletionList(const char *name,
+                                      const char *desc, const char *url);
 inline int AddToCompletionList(const char *name,
                                const char *desc, const char *url)
 {
@@ -274,6 +283,7 @@
 }
 
 /* Encode the given string so that {X}Emacs will understand it */
+static inline char *Encode(const char *s);
 inline char *Encode(const char *s)
 {
     unsigned int extra_len = 0;
@@ -341,6 +351,7 @@
 
 /* Output the completion list in a way {X}Emacs can easily read in */
 
+static inline int OutputCompletionList(void);
 inline int OutputCompletionList(void)
 {
     completion_list *cur = comp_list;
@@ -400,6 +411,7 @@
 
 /* Clean up */
 
+static inline void FreeCompletionList(void);
 inline void FreeCompletionList(void)
 {
     completion_list *cur = comp_list;
@@ -428,7 +440,8 @@
 }
 
 /* Add the members of a compound to the completion list */
-
+static inline int AddCompoundMembers(xmlNodePtr compound,
+                                     const char *name, const char *url);
 inline int AddCompoundMembers(xmlNodePtr compound,
                               const char *name, const char *url)
 {