[libc] Share hdrgen declarations between stdlib.h and malloc.h

libc/include/malloc.yaml

@@ -1,13 +1,17 @@
 header: malloc.h
-header_template: malloc.h.def
-macros: []
-types: []
-enums: []
-objects: []
+standards:
+  - gnu
+merge_yaml_files:
+  - stdlib-malloc.yaml
+macros:
+  - macro_name: M_PURGE
+    macro_header: malloc-macros.h
+  - macro_name: M_PURGE_ALL
+    macro_header: malloc-macros.h
 functions:
   - name: mallopt
     standards:
-      - GNUExtensions
+      - gnu
     return_type: int
     arguments:
       - type: int

libc/include/stdlib-malloc.yaml

@@ -0,0 +1,44 @@
+# This file has declarations that appear both in <stdlib.h> and in <malloc.h>.
+
+functions:
+  - name: aligned_alloc
+    standards:
+      - stdc
+    return_type: void *
+    arguments:
+      - type: size_t
+      - type: size_t
+  - name: calloc
+    standards:
+      - stdc
+    return_type: void *
+    arguments:
+      - type: size_t
+      - type: size_t
+  - name: free
+    standards:
+      - stdc
+    return_type: void
+    arguments:
+      - type: void *
+  - name: malloc
+    standards:
+      - stdc
+    return_type: void *
+    arguments:
+      - type: size_t
+  - name: realloc
+    standards:
+      - stdc
+    return_type: void *
+    arguments:
+      - type: void *
+      - type: size_t
+
+# Note: glibc's <stdlib.h> and <malloc.h> both have these, which are
+# currently missing here:
+#  - name: reallocarray
+#  - name: memalign
+#  - name: valloc
+# Each of those glibc headers also has related functions the other lacks.
+# Only the common subset is mentioned here for future consideration.

libc/include/stdlib.yaml

@@ -2,6 +2,8 @@ header: stdlib.h
 header_template: stdlib.h.def
 standards:
   - stdc
+merge_yaml_files:
+  - stdlib-malloc.yaml
 macros: []
 types:
   - type_name: __atexithandler_t
@@ -34,13 +36,6 @@ functions:
     return_type: int
     arguments:
       - type: int
-  - name: aligned_alloc
-    standards:
-      - stdc
-    return_type: void *
-    arguments:
-      - type: size_t
-      - type: size_t
   - name: at_quick_exit
     standards:
       - stdc
@@ -87,13 +82,6 @@ functions:
       - type: size_t
       - type: size_t
       - type: __bsearchcompare_t
-  - name: calloc
-    standards:
-      - stdc
-    return_type: void *
-    arguments:
-      - type: size_t
-      - type: size_t
   - name: div
     standards:
       - stdc
@@ -107,12 +95,6 @@ functions:
     return_type: _Noreturn void
     arguments:
       - type: int
-  - name: free
-    standards:
-      - stdc
-    return_type: void
-    arguments:
-      - type: void *
   - name: getenv
     standards:
       - stdc
@@ -145,12 +127,6 @@ functions:
     arguments:
       - type: long long
       - type: long long
-  - name: malloc
-    standards:
-      - stdc
-    return_type: void *
-    arguments:
-      - type: size_t
   - name: qsort
     standards:
       - stdc
@@ -182,13 +158,6 @@ functions:
     return_type: int
     arguments:
       - type: void
-  - name: realloc
-    standards:
-      - stdc
-    return_type: void *
-    arguments:
-      - type: void *
-      - type: size_t
   - name: srand
     standards:
       - stdc