Switch to g_ for globals.

That's what the Google style guide recommends, and we're starting
to get a mix.

Change-Id: Ib0c53a890bb5deed5c679e887541a715faea91fc
diff --git a/libc/bionic/debug_stacktrace.cpp b/libc/bionic/debug_stacktrace.cpp
index 4207a3f..713e761 100644
--- a/libc/bionic/debug_stacktrace.cpp
+++ b/libc/bionic/debug_stacktrace.cpp
@@ -50,30 +50,30 @@
 typedef _Unwind_Context __unwind_context;
 #endif
 
-static mapinfo_t* gMapInfo = NULL;
-static void* gDemangler;
+static mapinfo_t* g_map_info = NULL;
+static void* g_demangler;
 typedef char* (*DemanglerFn)(const char*, char*, size_t*, int*);
-static DemanglerFn gDemanglerFn = NULL;
+static DemanglerFn g_demangler_fn = NULL;
 
 __LIBC_HIDDEN__ void backtrace_startup() {
-  gMapInfo = mapinfo_create(getpid());
-  gDemangler = dlopen("libgccdemangle.so", RTLD_NOW);
-  if (gDemangler != NULL) {
-    void* sym = dlsym(gDemangler, "__cxa_demangle");
-    gDemanglerFn = reinterpret_cast<DemanglerFn>(sym);
+  g_map_info = mapinfo_create(getpid());
+  g_demangler = dlopen("libgccdemangle.so", RTLD_NOW);
+  if (g_demangler != NULL) {
+    void* sym = dlsym(g_demangler, "__cxa_demangle");
+    g_demangler_fn = reinterpret_cast<DemanglerFn>(sym);
   }
 }
 
 __LIBC_HIDDEN__ void backtrace_shutdown() {
-  mapinfo_destroy(gMapInfo);
-  dlclose(gDemangler);
+  mapinfo_destroy(g_map_info);
+  dlclose(g_demangler);
 }
 
 static char* demangle(const char* symbol) {
-  if (gDemanglerFn == NULL) {
+  if (g_demangler_fn == NULL) {
     return NULL;
   }
-  return (*gDemanglerFn)(symbol, NULL, NULL, NULL);
+  return (*g_demangler_fn)(symbol, NULL, NULL, NULL);
 }
 
 struct stack_crawl_state_t {
@@ -147,7 +147,7 @@
     }
 
     uintptr_t rel_pc;
-    const mapinfo_t* mi = (gMapInfo != NULL) ? mapinfo_find(gMapInfo, frames[i], &rel_pc) : NULL;
+    const mapinfo_t* mi = (g_map_info != NULL) ? mapinfo_find(g_map_info, frames[i], &rel_pc) : NULL;
     const char* soname = (mi != NULL) ? mi->name : info.dli_fname;
     if (soname == NULL) {
       soname = "<unknown>";