FR: header-only amalgamation

[GitMensch]

This could be done in three ways:

1. documentation only "how to create that (may include 2 and/or 3)"
2. release-only: a real single header file, created automatically (for example via Make) and uploaded to the release, either with a separate name like cjson_amalg.h / cjson_standalone.h or under cJSON.h
3. a single file stored in this repo - either with a separate name like cjson_amalg.h / cjson_standalone.h or as plain cJSON.h

The following works for a single-header wrapper:

#define CJSON_HIDE_SYMBOLS
#include <cJSON/cJSON.h>
#include <cJSON/cJSON.c>

along with the following

cJSON.h (which could be a separate condition, of course):

 #if defined(CJSON_HIDE_SYMBOLS)
-#define CJSON_PUBLIC(type)   type CJSON_STDCALL
+#define CJSON_PUBLIC(type)   static type CJSON_STDCALL
 #elif defined(CJSON_EXPORT_SYMBOLS)

cJSON.c (which possibly should be declared as static instead of nothing or CJSON_PUBLIC in any case):

 /* Duplication */
-cJSON * cJSON_Duplicate_rec(const cJSON *item, size_t depth, cJSON_bool recurse);
+CJSON_PUBLIC(cJSON *) cJSON_Duplicate_rec(const cJSON *item, size_t depth, cJSON_bool recurse);
 
 CJSON_PUBLIC(cJSON *) cJSON_Duplicate(const cJSON *item, cJSON_bool recurse)
 {
     return cJSON_Duplicate_rec(item, 0, recurse );
 }
 
-cJSON * cJSON_Duplicate_rec(const cJSON *item, size_t depth, cJSON_bool recurse)
+CJSON_PUBLIC(cJSON *) cJSON_Duplicate_rec(const cJSON *item, size_t depth, cJSON_bool recurse)
 {

Use case: mostly "closed" environments where I can't easily adjust the build system to include cJSON.c (=currently need to do it each time)