Adding new comment-matching regex to help license check with assembly files.

For example:
- third_party/ffmpeg/libavcodec/arm/hpeldsp_arm.S
- third_party/ffmpeg/libavcodec/x86/xvididct.asm

Review URL: https://codereview.chromium.org/1135243005

Cr-Commit-Position: refs/heads/master@{#329775}

third_party/devscripts/licensecheck.pl

@@ -342,10 +342,17 @@ sub remove_comments($) {
     $_ = $_[0];
     # Remove Fortran comments
     s/^[cC] //gm;
+    # Remove .ASM comments
+    s#^;\*?##gm;
+    # Remove .S comments
+    s#^@ ##gm;
+    # Remove new lines
     tr/\t\r\n/ /;
     # Remove C / C++ comments
     s#(\*/|/[/*])##g;
+    # Remove all characters not matching search
     tr% A-Za-z.,@;0-9\(\)/-%%cd;
+    # Collapse multiple spaces into single space
     tr/ //s;
     $_[0] = $_;
 }