Extend C to ignore Visual Studio artifacts

Visual Studio creates a few artifacts which weren't ignored before,
mainly .idb, .pdb and .ilk files which are either created by CL.EXE or
by LINK.EXE were added to the gitignore for Windows projects.

A little more information can be found here on Microsoft's
documentation: https://msdn.microsoft.com/en-us/library/3awe4781.aspx

C.gitignore

@@ -7,6 +7,11 @@
 *.obj
 *.elf
 
+# Linker output
+*.ilk
+*.map
+*.exp
+
 # Precompiled Headers
 *.gch
 *.pch
@@ -34,3 +39,5 @@
 # Debug files
 *.dSYM/
 *.su
+*.idb
+*.pdb