llvm-cov: Split GCOVFile's read into GCNO and GCDA.

This splits the file-scope read() function into readGCNO() and
readGCDA(). Also broke file format read into functions that first read
the file type, then check the version.

llvm-svn: 196353
diff --git a/llvm/tools/llvm-cov/llvm-cov.cpp b/llvm/tools/llvm-cov/llvm-cov.cpp
index 7f4d53e..b1ea33e 100644
--- a/llvm/tools/llvm-cov/llvm-cov.cpp
+++ b/llvm/tools/llvm-cov/llvm-cov.cpp
@@ -49,7 +49,7 @@
     return 1;
   }
   GCOVBuffer GCNO_GB(GCNO_Buff.get());
-  if (!GF.read(GCNO_GB)) {
+  if (!GF.readGCNO(GCNO_GB)) {
     errs() << "Invalid .gcno File!\n";
     return 1;
   }
@@ -61,7 +61,7 @@
       return 1;
     }
     GCOVBuffer GCDA_GB(GCDA_Buff.get());
-    if (!GF.read(GCDA_GB)) {
+    if (!GF.readGCDA(GCDA_GB)) {
       errs() << "Invalid .gcda File!\n";
       return 1;
     }