simplify isabspath from init.c and use it in dlopen instead of duplic…

…ating

src/dlload.c

@@ -137,12 +137,7 @@ static void *jl_load_dynamic_library_(const char *modname, unsigned flags, int t
         goto done;
     }
 
-#ifdef _OS_WINDOWS_
-    abspath = modname[0] == '/' || modname[0] == '\\' ||
-        (modname[0] && modname[1] == ':' && (modname[2] == '\\' || modname[2] == '/'));
-#else
-    abspath = modname[0] == '/';
-#endif
+    abspath = isabspath(modname);
 
     /*
       this branch permutes all base paths in DL_LOAD_PATH with all extensions

src/init.c

@@ -430,13 +430,9 @@ int isabspath(const char *in)
     if (c0 == '/' || c0 == '\\') {
         return 1; // absolute path relative to %CD% (current drive), or UNC
     }
-    else {
-        int s = strlen(in);
-        if (s > 2) {
-            char c1 = in[1];
-            char c2 = in[2];
-            if (c1 == ':' && (c2 == '/' || c2 == '\\')) return 1; // absolute path
-        }
+    else if (c0 && in[1] == ':') {
+        char c2 = in[2];
+        return c2 == '/' || c2 == '\\'; // absolute path with drive name
     }
 #else
     if (in[0] == '/') return 1; // absolute path

src/julia_internal.h

@@ -765,6 +765,8 @@ STATIC_INLINE void *jl_get_frame_addr(void)
 
 JL_DLLEXPORT jl_array_t *jl_array_cconvert_cstring(jl_array_t *a);
 
+int isabspath(const char *in);
+
 #ifdef __cplusplus
 }
 #endif